ED30 doesn't need any exterior mods. VW got that 100% spot-on at the factory.
As for the interior, knock yourself out. All manner of MK6/MK7 bits will bolt right in, although personally speaking, I prefer a car to be in period and original. I don't get the whole MK7 steering wheel and key on a MK5 thing. Just buy a MK7??
What you can do is fit MK6 chrome tipped window and headlight switches and leave it at that. I think newer steering wheels and climate panels just look out of place vs the rest of the interior, imo.