If more spell customization is ever added, this is definitely the way to do it.
2-3 personalized upgrades to the spell that emphasize both the magic type's identity and the spell itself's identity would dramatically increase build variety. It would be way too wordy to put all in one message (and honestly I haven't thought of a whole lot of ideas right now) but I will periodically update this post with my thoughts as to what each spell's overclocks would be (as well as justification for how this preserves the core identity of the spell)
Jokers also serve as a more blanket (yet customizable) building block for spell variety. This would be very similar to weapon jokers.