I'm a packdev and I've run into an issue where certain abilities that can be given to a focus end up breaking balance. I haven't really found a good way to take care of this. So my suggestion (hopefully it isn't too far beyond the scope of this mod) would for config options that would allow someone to lock certain abilities to certain foci or potential integration with gamestages so certain abilities could be locked behind certain gamestages.

Another possibility would be for players to be able to lock research behind gamestages.

I just realized some of these things I can already do (2am brain is fun) although gamestages compatibility should def be a thing

Just incase you didnt know you can use a mod known as "Thaumic Restriction" can restrict the abilities of most foci which isnt 100% what your looking to do but you might find some use out of it.

And secondly on the topic of gamestage support id say also including just base vanilla advancement support would also be very very helpful since base advancements have alot of possible things they can detect which can be very useful for more complex research

Hell, you could even add support for research to trigger commands which means they could give people gamestages, advancements or well do just about anything possible with commands including trigger datapack functions.

Vanilla advancements would be pretty easy to add support for, as long as they are of the "detect player getting advancement, give research key" variety - the other way around would be a bit more problematic.

I never used gamestages before, but it looks like they have an event API, so those would probably work as well.

I'm hesitant to add support for running commands because people probably don't expect configs to run commands, so that can turn into a security issue. If I do add that, it will probably be locked behind a config option that is disabled by default. Although I'd rather just add in support for things people need so that there doesn't have to be arbitrary commands running.

Having research give gamestages on top of locking research behind them would be a big bonus

Advancements and gamestages simply giving a research key would work fine in almost every case i can think of. And ya i can possibly see having configs being able to run commands a possible security concern so i can understand not wanting to add support for it.