Sounds like you needed to find a better profile cutter. Ive done a fair amount of profile cutting but have never been a fan of waterjet, can easily cut 10mm aluminium cleanly on the laser without needing to touch after. Bit more skill when you need to bevel cut
Wanting it cut from 12mm will require at least a 4kw laser, the old 3kw trumpf I use to run could do it but it wasnt that great and requires a bit of skill. Dont get it plasma cut.
You will need longer bolts, pretty much all vag cars after the mk2 golf are m14, longer for alloy wheels, dont forget to change back to the short ones for the steel wheels as the longer ones will catch
Pretty sure yours will be a cross flow, you would probably need the adapter for the midsection from a looper and the pan and cowling a different as well. Is yours a 20" or 25"?