TL;DR
This mod https://mods.factorio.com/mod/solar-productivity is perfect for what I want to explain here. It adds many entity prototypes called sp1-NAME, sp2-NAME etc. for every level of productivity. This can scale multiplicatively with other features from other mods and I believe it would be way more efficient and possible for the devs to add it to the base game since performance scales little to have a significant effect.Why?
I got an idea to make a mod that makes solar power deeper and richer to interact with instead of adding more recipes and complexity like most other mods do. However many feature ideas scale the number of entity prototypes multiplicatively: multiple tiers of panels and accumulators, combo mechanic which adds tiers of its own, productivity research which adds tiers of its own, adjacency upgrades which add tiers of their own (when an upgrader entity is adjacent to a solar panel or accumulator, it'll upgrade it similar to neighbor bonus of fusion reactors, but with more freedom). That's 4 different multipliers which forces me to either cut down the multipliers or the number of tiers per multiplier which let's be honest, nobody wants a productivity research up to level 3.I figured if it's added to the base game performance won't suffer because it scales with number of separate electric networks containing solar panel prototype and with the complexity of the calculation solar_panels * get_time_of_day_multiplier() * surface.solar_power * bonus.solar_productivity which is done once per electric network per tick. It's probably more complex than this pseudocode, but the devs have probably added more optimized systems to make it viable for per-surface multipliers.
Additionally while we're at it, if I convinced you to add this upgrade modifier type, consider also adding modifiers for the accumulators because my mod wants to do the same thing to accumulators with their tiers and upgrades, but it's worse because i want two adjacent upgraders, one for transfer speed, one for capacity so in total multiply accumulator entity prototypes by 1+2 or 1+3 if i allow both upgrades to stack. And i didn't ever mention a 2nd tier of upgraders, that'd really scale the entity prototypes out of control. (Nevermind, accumulators are easy, you only need an electric energy interface with 0 production, 0 consumption and you can update its buffer size once per research and once per placement of chosen entities.)