I'll be the first one.
For Maximum and Starting Value Multiplier - so you may limit it, or handicap yourself to engage more with the mod, as 31x feels a bit cheaty ngl, and starting multiplier being 1x makes this straight up PURE money gain, with no downsides at all.
For Blue and White spirit values - Goes well with previous one, allows for fully customizable balance and makes spirit gauge config better too.
Items you get from filling Life and Bomb gauge - Will allow to make these mechanics not obsolete after maxing out health or mana, as well as do some wacky stuff or make mechanic not get useless with some post moon lord mods and etc.
Upon maxing out the value multiplier, you can still increase it by getting blue spirits, but multiplier will slowly drain back to the maximum. The further you are from the set maximum value multiplier - the faster drain gets. Makes blue spirits not obsolete when multiplier and spirit gauge is full. Could be enabled or disabled, perhaps configured.
Spirit Pick Up Radius
Could make an accessory that increases pickup radius, or even make it into a config option. (Damn blocks hiding mah spirits...)
Penalty for Dying
Lose value multiplier for dying, so it's not always maxed out for the rest of the session. Config for it would be perfect.
Content?
Considering the prologue you made... would be really epic to have a whole story or just content that may back up the mechanic, with bosses, enemies and items that play around it. Gensokyo crossover when? :) Touhou modders should unite!