How slow of a spellcasting progression should a versatile at will caster get? [3.5]

[Temotei]

That's the point.

If 20 spells per day per level is balanced with at will casting then why not just use at will casting?

Couldn't have said it better myself (except I would have spelled out twenty, added a hyphen in at-will...etc. because I'm a grammar pirinazinja).

What at-will tricks can you think of that would not be quelled by my three limitations? (that way I can add a 4th)

Wish and miracle could probably get around them if you're allowing 9th-level spells. Limited wish might be able to if you're allowing 7th-level spells.