Does this Sorcerer homebrew feature have more efficient than intended uses?

Question

The following is a homebrew Sorcerer feature that is part of a Sorcerous Origin I'm experimenting with.

Wax & Wane

When you cast an applicable spell, you may choose to use the Heightened Spell Metamagic option for no sorcery point cost. You may do so even if you don't have the Metamagic feature yet or don't have Heightened Spell as a known metamagic option. Once you do so, you must finish a long rest before you can use this feature again.

Before you regain the use of this feature, if you cast a spell of first level or higher that forces one or more creatures to make a saving throw to resist its effects, those creatures make their first saving throw against the spell with advantage. You regain the use of this feature after the first such saving throw from the spell.

(Note: I refer to the first paragraph's effect as "Wax" and the second paragraph's effect as "Wane" below)

Additional context: I intend this as a first level feature as part of a homebrew Sorcerous Origin, hence the odd sentence about not having the Metamagic feature in the Wax description. I originally just duplicated the text of Heightened Spell for Wax's effect, but erred on the side of this being simpler & ensuring that the non-stacking metamagic rules apply.

I'm curious if there are any uses of this that are effective beyond my expected uses (enumerated below), or if there are any loopholes in the text that allow non-obvious means of use.

Expected potential uses:

1. Throughout combat, cycle between using Wax to boost powerful spells and then getting rid of the Wane effect by casting weaker/lower level ones.
   • Optimizable somewhat by targeting enemies with lower saving throw bonuses with Wane'd spells.
   • Note: This is more or less the 'main' intended use, with the sorcerer counterbalancing strong Wax turns with followup low-impact Wane turns that still require burning resources.
2. Use Wax once at an appropriate time, then use non-saving-throw spells for the rest of the day.
3. Use Wax on your last level 1+ spell of the day.
4. Use Wax in combat, then get rid of the Wane effect later out of combat on an ally/critter/easy fight to avoid losing an important combat action on it and (more or less) wasting a low level spellslot to do so.

Note that I'm specifically not asking about the general balance quality of this at the moment, though if that's relevant to your answer feel free to include it. I'm just trying to find out if there are any holes in my expectation of how it would be used.

Answer 1

It is too powerful, particularly at higher levels.

You asked if the feature can be used in unintentional ways or holes and the answer should not be focused on balance, but as a matter of fact. The biggest issue that I can find is that it theoretically breaks the caster/slot economy at higher levels for an extremely low price. For a Sorcerer, this is not a big deal, since she has metamagic on her own, but this can be highly abused by other classes as a one dip thing. This in itself may be an unforeseen consequence rather than a balance issue (a hole if you wish to say).

Spell economy

Having advantage on a spell is similar to casting that spell twice at the same time, with the only caveat being one can hit, but the other is useless. At low levels this seems balanced since the caster's spell repertoire and lack of slots is a deal breaker. At high levels though, with so few high level spell slots but many low level spells to offset, the Wane is simply too good.

As a Wizard

What is not to like about this feature? If I start as a Sorcerer, I start with CON saves, I don't lose spell slots, I get some spells that are always prepared magic-book free, and more cantrips that I can cast. The price? being one level behind on spells levels (but not slots).

Also, as a wizard I have Arcane Recovery. This allows me to recover tons of low level spells at higher caster levels. Highly abusable for a mid-high level wizard. And with some of the wizard features like Spell Mastery and with the right spells, you can abuse this all day long; Phantasmal Force is a great one to offset Wane. If it fails at least is not different from a Fighter missing an attack. If it succeeds, it is a force to be recognized. It also can be cast at your allies outside of combat. Make your friend see a sexy devil and he'll be happy to help you with the Wane (wink, wink).

Similar with other classes

Valor Bards and Blade Warlocks will benefit a lot of this feature, particularly after they get their second attack feature. For Warlocks, this means more spells to cast, more cantrips, and a feature that increases their casting economy by leaps. This is particularly true for any save or suck build.

The main problem is that it does not have diminishing returns, but it becomes better the more caster levels you have, mainly for a non-Sorcerer class.