Experiment: Omnisystemic Games

I've had this idea for a while. It's not good, it might even be stupid, but it's interesting and I want to try it anyway.

I call it an omnisystemic game.

The idea's straightforward: Run a system-agnostic adventure and let your players make their characters with any system they want, as long as it's one you feel comfortable running. So you might have characters from OD&D, 5e, bastards., Troika!, DCC, MoSh, WoD, whatever all at the same table. Run the game for them and switch between their separate systems on the fly when each character interacts with things in a way that would require rules to resolve.

The rules for each system would only affect the characters from that system. So Troikan characters would use Troika!'s token-pull initiative while 5e chars would roll d20+initiative for a turn order. Only DCC characters would use the dice chain. bastards. characters would have advantage/disadvantage while WoD chars would gain or lose dice from their pools. Difficulties for checks/saves/ACs/etc would shift depending on which character's acting to reflect what's reasonable for their system.

You would essentially be running [X] many different games at once depending on the number of systems your players chose. Each set of rules running in parallel with specific chunks temporarily being pulled to the fore when a character acts and then going back into standby after everything's resolved. It's what happens if you take system agnostic way too far, following the letter while obliterating the spirit.

I want to try and find out:
- Can I actually do it?
- How hard is it?
- Is it actually different from a normal one-system game in any appreciable way beyond (maybe) taking extra effort?

I think I can do it and I don't think it'll be that difficult. Converting the adventure into the different systems on the fly would probably be the most demanding part, and that seems like something you'd get used to with some practice. Just paying attention and staying flexible, which you're already doing as the GM. Might be a little more improv intensive than normal but it'd only be an issue when rules actually come up or you need a ruling, and you'd just have to remember who's using what system. Having players who know what they're doing (and I always assume mine do, trust your players) would also take a lot of the work off the GM. The thing I'm almost entirely unsure about is if it's worth it.

We'll see how it goes once I find a group of players willing to go along with my shenanigans. If you want to try running something omnisystemic good luck and let me know how it worked.