You know, TM does make an actual full size UZI.
Though I don't think it's much for upgrades (IE. No heavy spring upgrades, the gearbox won't handle it), it will outdue the MP7 in most if not all ranges and it is battery opertated, not gas. Likely cheaper too.
Have you looked into that? There is a review on Arnie's.
http://www.arniesairsoft.co.uk/?filn...uzi_review.htm
The MP7 won't compete well against AEGs, other than indoors.
The KWC is just too powerful. You wouldn't be able to use that on any field in Canada.
As well as that, the CO2 cartriges do cost about $0.75 per... if you're only getting 30 or so shots, it will greatly increase your costs.