The problem is, the tried and tested method is usually the most cost effective, and thats why its the tried and tested method.
As an example, a while back i looked into making something like the common 17Z setup, but using standard B5 hubs. I bought some Megane 225 brembos as they had the correct size pistons (unlike the porsche calipers), and a 320mm A5 brake disk and tried to mount it all up onto a standard B5 upright. The offset difference meant the brake disk touched the caliper mounting lugs on the upright, and there was simply no way it was going to work. I could probably have found a lower offset disk, but i was trying to make it all fit inside the standard wheels, and the extra bulk of the 4 pots plus the shallower disk would have stopped that from happening. In the process i'd also wasted a load of cash. I sold the brembos on, but ofcourse got less than i paid for them, and the disk was unboxed and marked etc from test fitment so that was unreturnable and i ended up selling it on ebay for 99p.
I realised that if you shop around and be patient on ebay, you can buy the correct later model uprights for peanuts, way cheaper than what it would have cost to have bespoke adaptors made up to fit the brembos. I paid £30 each for the front uprights from a 2003 A6, and when you've done that you open up the whole world of off the shelf upgrades that fit later models.
If you really do want to try something yourself, then i'd suggest trying some Merc C320 Sport brake disks, and the megane 225 calipers. I cant guarantee it'll work, but the meganes are cheap enough, and the C320 Sport disks are the correct thickness for the caliper, and should fit the upright as they're a little shallower than the ones i tried.