I'm taking a different approach on my next playthrough

[Crossblades]

Terra and Celes learn some magic on their own, without espers. Since you said Terra will use both black and white magic, her learning fire spells won't affect your strategy, but Celes will learn ice spells, and you wanted her to be a white mage only.

As far as the strategy, go for it. It sounds interesting.

Celes will be more of a Paladin than a White Mage(Relm will take over that role since she'll also learn White Magic and will have Time Magic as well and Time Magic is sometimes considered White Magic in other FF games. Also Celes will have relics that make her seem Knightly, like the True Knight relic.) But Celes learning some other Magic can't be avoided, unfornately. So I'm just gonna have to deal with it.

Also, I have made a tiny change to my strategy. At first I was considering Edgar to learn Time Magic, but I changed my mind now. I'm just gonna give him Dragoon boots and Dragon Horn relics to make him into a Dragoon and also have him stick with Tools