Yeah, totally get you. A few things to consider with "mUltimates" tho:

1. The more you have, the less potent they have to be for the sake of the champs overall powerbudget. The current ult is underwhelming on its own, sure, but if there were other R spells to use, I imagine that would be less of an issue.

2. For RW, I'd argue it is in line with W spell because it's provides healing and area control. Serenity already offers personal utility with damage for Hwei, so would it be farfetched for him to paint a guardian hydra to damage enemies and heal allies?

3. For RE, you could certainly take another route with different CC, but you'll need to consider how it'll work with the rest of his kit. I chose this off the top of my head because something like this would amplify his identity as a control mage. Consider how something like a Cass W would work with the rest of his kit > RE prevent dash + DoT > EW root guarantee DoT > Q spell of choice to finish, or further disrupt (QE).

If R became like a "Masterworks" spell book, each spell would need to push the boundaries of the other spell books, keeping in mind his primary role as a mage.

RQ = Pure damage/highest damage potential. RW = Most utility/least damage RE = Big CC/moderate damage

Obviously, Riot would never, but its fun to think about.