If they are requiring an = they aren’t spec compliant? 
But agree, we don’t want to break anything. This is pretty easy to verify, though, since we have a good list of implementations listed at https://bitcoinqr.dev/ which can be used to verify, and this is a somewhat trivial fix if they are requiring an =.
This seems less risky then specifying bitcoin:?key=val, which seems more likely to break existing implementations since a spec compliant implementation would expect an address in the root of the URI.
Furthermore, this can be used along side existing key=val parameter pairs, so you can even start using the new technique along with the old way in a backwards compatible way. Seems like a no brainer to me.