ICS has a full line of replacement front end bits and stocks, so there's good choice. But most mp5s seem to have their own quirks in their own manufacturer families.. g&g went their own way, but ics and CA are almost completely tm spec. CYMA is semi tm and have some of their own parts. Just pay attention to if your mp5 has an outer barrel under the handguard or not, that seems to be a major determining factor in finding compatible front ends.
the G&P handguard will fit the ics though, I have one sitting in my parts box that was previously on mine.
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.