Description:
Let players “patch” or upgrade an existing custom engine to add new features, instead of always having to develop a whole new engine. This would cost less money, keep the engine’s popularity bonus, and help keep the engine list uncluttered. This system is ideal for late-game studios who want to stay competitive without having to spam new engines for every new feature.

Key Features:
Players can add new features to an existing engine with a “Patch Engine” button. You only pay for the newly added features, plus a small flat fee. Patched engines keep their popularity and do not reset. You have the option to rename the engine, for example changing “MyEngine v2” to “MyEngine v2.1.” There is no need to recreate an entire engine from scratch for minor upgrades. This only works with engines you own, not licensed ones.

Why This Mod?
Currently, adding even one feature means you have to make a brand new engine, which costs a lot of money, fills your engine list with near-duplicates, resets engine popularity, and becomes tedious late-game. With “Engine Patches,” players can modernize their engines in a cleaner, more realistic, and much more convenient way.

Balance Suggestions:
There could be a limit on the number of features per patch or a cooldown between patches. Patched engines could get a small, temporary popularity boost, or at least keep their old bonus. There could also be a flat fee added on top of feature costs for balance. Another possible balance idea is to limit the total number of patches you can apply to a single engine before being required to create a brand new engine. This helps prevent endlessly upgrading the same engine and keeps the upgrade process meaningful.

Is this possible?
Other mods like CheatMod and UltimateLib already interact with engines and features, so this should be technically possible with the current mod API.