Welcome, I've not heard of the gun mentioned, that could be a good or a bad thing, but someone will be along soon to enlighten us.
As for altering an m4, why, when there are already lots of stubby models available off the shelf (& often in the classifieds here), & they'll be set up to perform pretty much at the best of their abilities.
Alternatively there are plenty of other models available with short foregrips & sliding stocks, mp5k pdw's, G3 sas or mc51 immediately come to mind, I'm sure there's lots of others.
Edit: since posting, I had a quick skim in the classifieds here:
https://airsoft-forums.uk/classifieds/category/4-electric-rifles/
First couple of pages saw loads of possible contenders, & at good prices for a starter gun