Is this "Slowed Spell" metamagic balanced?

Question

I was thinking about the uses of the Sorcerer's Quickened Spell Metamagic option and came up with my own metamagic: Slowed Spell:

When you cast a spell that has a casting time of 1 bonus action, you can spend 2 sorcery points to change the casting time to 1 action for this casting.

This would allow them to cast a spell that usually requires a bonus action and then use their bonus action on something else.

I am wondering if there are balance issues that arise from this versatility. Some potential problems I thought of:

1. The spiritual weapon spell could make two attacks on the turn you summon it (the first from it being cast as an action and the second when you use your bonus action). However I am unsure if this is a problem as the Quicken Spell Metamagic already has the opposite effect: Spells like witch bolt can be quickened so you can activate their action effect on the turn you cast them.

2. The effects this would have on the War Caster feat. This new metamagic would allow you to cast spells that usually require a bonus action (and thus usually can only be cast in your own turn) to be cast as actions, qualifying them for War Caster and thus allowing them to be cast even when it is not your turn.

3. Other combinations, such as using Flexible Casting to make a spell slot on the same turn you cast a bonus action spell. Or casting spiritual weapon on the same turn you enter rage. Really any similar things that result from the ability to effectively have two bonus actions on a turn (though at least one must be a spell).

Note: I do not particularly care if the Sorcerery Point cost is balanced (and believe actual playtime would be the best show of that). I mostly care if having this as an option makes for some unforeseen effects.

Is this Slowed Spell Metamagic balanced?

Answer 1

It is balanced in almost all situations

From my experience, the only potential problem with this Metamagic is when a Divine Soul Sorcerer uses it with spiritual weapon at low levels, where the spell is stronger.

I played two one-shots where the DM had a house-rule that allowed bonus action spells to be cast using an action, and both times, the group had a Cleric – the turn when he casted spiritual weapon usually "unbalanced" the combat because of the high burst damage it provides (4d8 + 2*Wis if spiritual weapon is cast at 3rd level, for example).

About the interaction with the War Caster feat, only a Divine Soul can use it, as none of the Sorcerer spells with a casting of a bonus action can be used with War Caster (possibly Dragon's Breath qualifies, but Crawford discussed this once). Also, the only option for a Divine Soul Sorcerer to use this combo offensively is with Divine Word, as Spiritual Weapon can't be used in this way – it targets a point within range for where you summon the weapon (this can be discussed, and the DM can always make a ruling).

The War Caster feat is clear (emphasis mine):

When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only that creature.

Other possible interactions from this is that you can cure or buff your enemies when they provoke opportunity attacks from you, as the healing word, shield of faith and sanctuary spells qualify for War Caster when used with this Metamagic option, but you certainly don't want it.

If gain some bard levels (which can potentially access any spell in the game), the other options for War Caster are compelled duel, hex, and hunter's mark, which aren't game breaking (although compelled duel can be very good). Overall, bonus action spells don't combo with each other, because the majority of them require concentration, so it should be fine.

Answer 2

No, It's a Trap

I believe that this metamagic option is overly niche and weak. Usually, casting a spell as a bonus action would be an advantage - stripping this away is hardly worth one of your limited metamagic slots, let alone 2 SP.

I believe that you have already highlighted the niche case where this might be used - to allow you to hit twice with a bonus action reproducible spell, like Spiritual Weapon. Keep in mind Spiritual Weapon only does 1d8+SpellMod to-hit/damage [or 8.5 average, given a +4 modifier]. Compare that to Toll the Dead, which does your Spell DC or 1d12 [6.5 avg] damage most of the time at levels 1-4. On levels 5+, your cantrip clearly does more damage than the Spiritual Weapon. The minimal difference in damage on levels 3 and 4 is hardly worth 2 SP (valued at approximately one level 1 spell slot) and a metamagic slot.

Your group is fairly low-power if a Level 5 cleric attacking twice with a Spiritual Weapon (2*(2d8+4) [26 avg] using a level 3 slot) is a balance issue. Rangers at L5 can pull off (3*(2d6+3+10)+1d8 [64.5 avg]) damage per round without expending resources other than Hunter's Mark, with the right feats, and no magic items. A quickened Fireball and Toll the Dead does ((8d6)+(2d12) [41 avg]) for comparison when considering any L5 sorcerer, and most of that is in an AoE. Not to mention that you're actually likely to get more bang for your buck in most parties by casting Bless or Twinned Haste if you're going down that road.

Your bonus action is usually just that - a bonus. The bulk of your contribution to the fight usually (but not always) comes through your Action. Generally, your feat would mean giving up your cantrip (which usually does comparable damage to Spiritual Weapon in the first place), or some other action (Dodge perhaps?) in order to hit again with your mediocre Spiritual Weapon.