Comment by gus_massa

I agree.

The closest example I can remember is that you can have atoms with muons instead of electrons for a shot time ~2.2E-6 seconds, that is a pretty long time for for an unstable particle. You can do some chemistry in that "long" time. (Can you put a muon around a heavy atom like gold and get some extra time for special relativity corrections?)

If you want to replace protons, I guess you can try with "strange" particles instead of "charmed" particles. The difference of mass is small, like only a 10% more instead of a x4 increase. In particular, the sigma particle (up+up+strange) has a half life of ~2E-10 seconds that is shorter than the half life of a muon but much longer that the half life of this new particle. (I can find the number, but let me handwave a ~~~1E-22 seconds(???).)