The VFC HK416 is a good gun, there are some better ones out there, but it's a solid choice. If you're looking to polarstar it later, it's a great choice because it has great quality externals, and the fusion engine was actually based around the VFC HK416 CQB, so it'll fit like a dream.
Didn't know that about the 416... Even if it wasn't the base for the fusion engine it would be a good gun!