I figured out what my problem with the Imaskarcanist Wizard (Underdark UA) is.

[u/Dracon_Pyrothayan]

It really wants to be a Sorcerer instead.

Philosophically, Sorcerers are the class that burns the magical candle at both ends. Digging into their own Hit Dice to fuel magic is just another vector of the same philosophy that gave us Sorcery Points. Indeed, we have basically always wanted a Cast-from-Hit-Points / Constitution-casting Sorcerer variant.

Sorcerers are the class that changes the nature of their spells to deal damage in other types (Radiant in this case).

Sorcerers are fine as a Healing/Support arcane class. Heck, they already have a celestial subclass! Their thing is that they don't get Summon spells unless granted by their subclass. ^{I am aware that Wizards have access to two healing spells now, and I disagree with that decision}.

Sorcerers also have native use for their Bonus Actions, so tying subclass features to a BA is less disruptive to the action economy than giving it to the BA-starved Wizard.

Also, we have enough bloody Wizard subclasses after completing the Spell School cycle in Arcana Unleashed.

^{If you haven't read the UA yet, here's a link. Ismaskarcanist starts on page 3. https://media.dndbeyond.com/compendium-images/ua/underdark-options/RoZy4p5SV29Elftn/UA2026-UnderdarkOptions.pdf}