How can an ultimate magus control spellcasting progression when Practiced Spellcaster isn’t enough?

Question

A background in the ultimate magus class and how it progresses spellcasting

An ultimate magus progresses a prepared-spellcasting arcane class and a spontaneous-spellcasting arcane class at each of 2nd, 3rd, 5th, 6th, 8th, 9th, and 10th level. At the other levels, 1st, 4th, and 7th, it advances only the arcane class that has the lowest caster level. Due to skill requirements, one’s first level in ultimate magus cannot happen before character level 6th. A typical entry is, for example, as 1st-level beguiler/4th-level wizard.

Wizard spellcasting is better than beguiler spellcasting, and having the highest-possible level of spellcasting is more important than having balanced spellcasting for each. It is therefore valuable to try to advance wizard as much as possible, despite having more levels in that class to begin with.

Because which class it advances at 1st, 4th, and 7th is keyed off of the caster level of the classes, it is possible to manipulate which class gets advanced. For example, if the aforementioned 1st-level beguiler/4th-level wizard has Practiced Spellcaster (beguiler), they have beguiler caster level 5th, not 1st, so when that first level of ultimate magus is taken, the class with the lowest caster level is actually wizard, not beguiler. Likewise, when the 1st-level beguiler/4th-level wizard/3rd-level ultimate magus takes the fourth level of ultimate magus, the caster level of beguiler and wizard are each 8th (4 wizard levels + 3 ultimate magus levels + 1 spell power and 1 beguiler level + 2 ultimate magus levels + 4 Practiced Spellcaster + spell power), and in the event of a tie, the ultimate magus can choose—and so chooses wizard again.

But the 1st-level beguiler/4th-level wizard/6th-level ultimate magus has a problem. Since Practiced Spellcaster offers a bonus of +4 at most, and cannot be taken again for the same class, their beguiler caster level is only 11th (1 beguiler level + 4 ultimate magus levels + 4 Practiced Spellcaster + 2 spell power) while the their wizard caster level is 12th (4 wizard levels + 6 ultimate magus levels + 2 spell power). Since 11th is less than 12th, ultimate magus would force this character to advance beguiler.

Even worse, in another answer I suggest a 5th-level wizard/1st-level assassin/10th-level ultimate magus. Because this involves five wizard levels instead of four, the problem occurs at the fourth level of ultimate magus, instead of seventh level, and by 10th level the assassin needs to make up 2 caster levels instead of just 1.

The question

So my question is this: what options exist for improving the caster level of one class, but not another, that are sufficiently permanent¹ to apply during level-up so that ultimate magus continues to “pick” wizard over beguiler or assassin or whatever in these situations?

Methods that cost wizard spellcasting to achieve are not useful here (the whole point is to maintain wizard spellcasting progression), so I expect that class levels will not be involved in any solution. Likewise, races with RHD or LA are going to have less wizard spellcasing and are not desirable. Answers are welcome to surprise me on these points, though, so long as wizard spellcasting progression is maximized.

Methods that require higher levels are acceptable so long as they can happen before one takes the 7th, (better) 4th, or (best) 1st level of ultimate magus while still allowing one to take all ten levels of ultimate magus by 20th. The rules of the Epic Levels Handbook are not in play in any capacity.

If options exist only for particular class combinations, such as something that will improve sorcerer caster level but not assassin or beguiler, or will allow a wu jen to continue receiving progression but won’t work with a wizard, I am interested in these and would like to see them, but please make sure they are clearly marked.

1. _{I leave the definition of “sufficiently permanent” up to you, but please note any tight level-up windows that a particular approach requires. Answers that offer options without such limitations are much preferred over answers that lack methods without such limitations.}

Answer 1

An Illumian with the Krau Power Sigil, at level 2, has a +2 CL, up to his character level, that should stack with Practiced Caster.

This is sufficient to solve the problem entirely for both the Beguiler 1/Wizard 4 entry, the Assassin entry.

Side notes:

1. If you take the Enhance Sigil feat, you can mitigate one additional level.

2. While the Krau bonus affects Wizard too, the way the bonus adds "up to your character level" means that both caster-levels are always equal for the relevant examples given by the question. And when the caster-levels are equal, the player gets to control the choice, which is the desired goal of this question.