Probably not the best idea even if your need more than one of them to spend.
If your going to the trouble of using Multi-Sig then why keep the keys online?
Seems pretty stupid.
Im only talking about keeping the Zpubs online, you can't spend with just Zpubs. you also need the private keys which of course would not be stored online. Im curious if there are risk involved with storing public keys(Zpubs in this example) online.