If I just wanted to add a spell to the Player, I just need to make a barebones quest set to Start Game Enabled with one lone alias for the Player with the intended spells... right? I am finally getting around to auto-adding the "Dragonsoul Boost" effect in my Dragonborn Ascendant mod, now that it dawned on me that quest aliases can do it. No hidden landmines to step on by doing this?

Nope, in fact it is probably the best way to go about it.
EDIT: Check allow reserved.

Errr.... "Allow Reserved" is grayed out.