Today most systems of goverment are shaped more or less the same:
2 chambber parliament, suprem court and either a President or a Prime Minister as executive. Even dictatorships pretend to be that way, maybe slapping a military junta on top.
There are only a few exceptions left, like Switzerland and Iran
How could other systems survive / be more prominent (without unneccasary social changes) like:
Sun-Ya-Tsens system, Bonapartes 4 +x chamber system, medieval spain with all its regidores and alcades, a working councils-democracy, consenus democracy, parliaments without an independent executive, privy councils as the true centres of power, the old Dutch Republic ...
Further examples welcome.