One thing about the M27 vs SAW debate is that you can't clear a room with a SAW, leaving its user at a clear disadvantage in urban combat. They're still retaining SAWs for when their capabilities are required, though. The M27 isn't a replacement for
all SAWs, as is commonly believed.
On the topic of the XM8, I could have gotten behind the last version made.
But it just came too late in the program. I would say all it needs would be to extend the side and underbarrel rails further back, an AR-compatible magazine well, AR pistol grip adapter, and side-folding buttstock.