Having prerequisite values for upgrades is an interesting idea. I like that it aligns well with the concepts that have been brought up that featured intermediary steps between unlocks/upgrades. However, I’m rather indecisive about the idea, as while it would be a great way to make upgrades be more progressive and gradual, it could potentially hinder players from doing all that they want.
Take the flagellum upgrade concept you posted for example. If a player had a longer flagella but wanted a longer cilia; Would they have to push the slider down to the required levels, change to cilia, and then move back to the peak longer area to get what they want? I think in this case, I would prefer to have the upgrades be independent from the sliders.
That being said, I recognize that that leaves a bit of a void where you might want that gradual sense of progress, so I have an idea to pitch for that. Rather than being able to immediately upgrade a part to the next form at a flat cost, we could instead allow the player to invest any amount of MP they want into the upgrade they want. The invested MP would be saved between generations, and would allow the player to gradually buy an upgrade at whatever pace they choose; whether that be dedicating all their MP in one session, or simply using the leftovers from other changes.
Infact now that I’ve said it I think that could actually be a decent way to handle organelle unlocks if we like this concept.
Sorry about being so late to reply by the way, I’ve been busy with college lately and I’ve found my motivation to be lacking as of late.