If the delay were removed, within a week, some industrious code monkey will release a third-party tool that exploits the lack of a delay.

Gaining TP? Equip Triple Attack, Dual Wield III, Accuracy Bonus, and Store TP.
Doing a self-skillchain? Drop those unnecessary Dual Wield spells, and add Skillchain Bonus.
Casting a nuke? Who needs Store TP and Triple Attack? Swap those out for Magic Attack Bonus, Fast Cast, and Conserve MP.
Rotate as needed.

I don't even know why I'm bothering to present a counter-argument. I don't think developers would do this. People seem to forget that these mechanics aren't put in place simply to make us miserable. ... Well, in most cases.

I wouldn't mind seeing a new iLvl ammo item or something that increases our spell capacity in some respect, similar to the tiers of avatar level increases in new SMN gear, but I don't really think it's necessary. Maybe, when you're soloing, you'll be able to equip some more debuffs without dropping offensive traits, but we're already one of the most solo-friendly jobs out there. Party play isn't going to change at all.