Just a quick run-down of the choices already made and suggestions in the question.
Lost Traditions is amazing
This feat is fantastic; I would not allow it in my games at all. This character can get away with a lot of “mistakes,” build-wise, because this feat is so beefy. So take the following with that grain of salt; the critique applies, but ultimately you’re starting from such a good place that you still wind up quite strong.
Battle Sorcerer is bad
Battle sorcerer permanently stunts your spellcasting, but only improves your sorcerer class levels. You will want to take prestige class levels instead of sorcerer levels as much as possible, so most likely you will have a maximum of five sorcerer levels. This is a difference between BAB +2 and BAB +3. The increase in HD is minimal and half replaced by dwarven sorcerer, the weapon proficiency is likely to be replaced by prestige class selection (and only represents a +2 damage increase anyway), and the armor proficiency and armored spellcasting can either be replaced or don’t matter since you can trivially wear armor anyway. So really only the +1 BAB is significant here.
Losing a spell known of every spell level is not worth +1 BAB. The only time battle sorcerer is recommended is when the extra BAB gets you into a prestige class earlier.
Wizard would be dramatically better
To begin with, wizards just are better than sorcerers; wizard spellcasting is dramatically more flexible and forgiving. Wizard spells per day look similar to sorcerer spells known (and specialist wizard spells per day look a lot better than battle sorcerer spells known), meaning that while the wizard has to plan for the next 24 hours, the sorcerer has to plan for the rest of his life.
Furthermore, the wizard is just better for this character. They can trade their bonus feats for fighter bonus feats; this enables a wizard to, e.g., pick up Martial Weapon Proficiency or Armor Proficiency. That goes a long way to replacing battle sorcerer’s flavorful components, and eases entry into prestige classes that will dramatically improve prowess in melee. Moreover, the excellent dwarven prestige class runesmith, from Races of Stone, requires that you prepare spells ahead of time anyway, so to enter it as a sorcerer (already more difficult due to the lack of bonus feats) is to give yourself the worst of both worlds as far as spellcasting goes.
Earth Bloodline is OK
Nine spells known is pretty solid for a feat, though none of them are all that impressive. Losing all [Air] spells kind of hurts, but honestly only wind wall is coming to mind as a significant [Air] spell and it’s not that significant.
Note that, if I did convince you that wizard is superior, they can arguably still take Earth Bloodline by taking the Spontaneous Divination option from Complete Champion, which is by no means a poor option in its own right.
Alternatively, Arcane Disciple from Complete Divine could get you the Earth Domain’s spells instead; they don’t become spells known, so you’d have to scribe them into your spellbook, but for a wizard that’s cheap and easy. This is also better for a prestige class I will recommend later.
Shielded Casting is just about completely pointless
This character should have massive Constitution and maxed ranks in Concentration. Defensive casting checks are really easy. The character will probably succeed even on a nat-1 by like, level 7 or so. Even at 1st, it’s a fairly safe check. Not a great use of a feat.
Becomes much better if you expect to run into people with the Mage Slayer feat often.
These are my actual suggestions. I am going to assume that none of the above critique has actually changed anything, however, and assume we’re dealing with a battle sorcerer with an Earth Bloodline.
Abjurant Champion (Complete Mage)
Every arcanist who ever wanted to swing a weapon should take this class. Entry is relatively easy:
- +5 BAB
- Combat Casting
- 1st-level spells
- Proficient in at least one martial weapon
This means that, as long as the battle sorcerer takes Combat Casting, he or she can qualify at 7th and take his or her first level at 8th. Finally, something the battle sorcerer is better at; a wizard (or non-battle sorcerer) would have to wait until 10th to qualify.
Anyway, the class is 5 levels long, and offers
- Full spellcasting progression for 5 levels
- Full BAB progression for 5 levels
- Various improvements to abjurations that improve AC
The first two are the big ones; note that mage armor is not an abjuration, and then ask your DM if he’ll make it one since even the authors of Complete Mage thought it was (the example abjurant champion is statted as if it was), and it really should be. If not, luminous armor and greater luminous armor from Book of Exalted Deeds are abjurations, and are better than mage armor, but are also higher level, hurt you when they finish, and require that you be Good.
Earthshaker (Dragon vol. 314)
This prestige class is an excellent choice. The requirements are a bit tricky:
- Knowledge (dungeoneering) 6 ranks
- Knowledge (nature) 12 ranks
- Ability to cast soften earth and stone
- Ability to speak Terran
As should be immediately obvious, wizard is once again superior, since they get those Knowledge skills. A sorcerer can take the Educated feat (Eberron Campaign Setting) to get all knowledge skills always-in-class, which is nice-ish. Knowledge Devotion is a far better feat, but only gets you one knowledge skill; you could do cross-class ranks in Knowledge (dungeoneering) if you wanted, but you’re going to have very poor skill points per level as it is, since sorcerers only get 2+Int skills and you have no particular use for Intelligence. That said, it can be done.
As for casting soften earth and stone, you can do this, as either class, by taking Arcane Disciple for the Earth Domain, which includes soften earth and stone. Since Arcane Disciple for the Earth Domain gets you entry, I would ask the DM if the Earth Bloodline can get you entry. Maybe call the requirement the ability to cast stone shape? As a 4th-level spell, that’s a generally much harder spell to cast, but it’s on the Earth Bloodline and since 12 ranks requires 9th level anyway it won’t matter much.
Anyway, once you get in, you gain the following benefits:
- Full spellcasting progression for 10 levels
- ¾ BAB progression for 10 levels
- Earth Domain
- See Complete Divine for the rules for gaining a bonus domain as a non-cleric.
- Try to convince the DM to overrule it and allow the domain to add directly to a sorcerer’s spells known. Otherwise it’s not worth much.
- Tremorsense that scales with class level, eventually out to 25 ft.
- Tremor and Greater Tremor, which shake the ground in an area around you, knocking enemies over; decent enough.
- Geyser, which does exceptionally minor damage, but has a chance of shoving creatures away from it and knocking them prone, which is pretty awesome.
- Earthquake as a spell-like ability, first 1/day then 2/day.
Really, the benefits of this are primarily in the full spellcasting at ¾ BAB; the rest is just fluff – but fitting fluff.
Final Build – Battle Sorcerer 7/Abjurant Champion 5/Earthshaker 8
It’s a shame we can’t get into earthshaker (or abjurant champion) earlier; Sorcerer 5/Abjurant Champion 5/Earthshaker 10 would be a far better and neater build. Talk to your DM about easing some of the entry requirements, particularly the skill requirements on earthshaker.