If by doing it right means finding a good chassis to start and building it right, I would get a manual trans A4 quattro 1.8t AEB.
Forget leaving the bottom end stock. The parts and prices have come down on building 1.8t’s with all the recent 2.0T support out there.
Tried and trued IE forged rods, $350, JE forged pistons & rings $400, ARP head studs $150, Eurospec main studs $150, $300 in gaskets, msc bolts, timing belt and dowel pin kit for the crank. $1300 builds you a stout bottom end. You could even just do the drop in IE rods with the stock AEB pistons (slightly stronger than the AWP shits) and do it all with the car on a lift and not touch the top end saving a ton of time and money.
3071 on it, 25psi, 044 or even a walbro 255 inline, stock intank, 630cc injectors, 350hp or so. Leave the AEB head stock. Keep the turbo choice around a 4000K spool and let it rev to the stock 7500 redline. The VW boxes are decent at keeping the upshifts from redline to around the 4000rpm in the next gear, put a WOT box in it and never come out of boost on upshifts. It would make a fun car for sure, and get 35mpg. Unitronic or Eurodyne tune deletes SAI pump that always die, EVAP that always leaks, MAF, secondary 02 so you can run full catless, and best of all all readiness monitors are HARDSET to pass… so no worries at all trying to pass inspection.
The 1.8t I built in mine with the 3076 @26psi was an absolute blast. In an AWD car that could hook less than 3rd gear like the jetta did, would be very very quick.
You could also go nutty on it too and do a stroker 2.0L+ 1.8t based motor, put valves and springs in the head, cams rev it to 8000 or a bit more, 67mm BB turbo or bigger, and make 500-600hp rather easily.
Most here is good other then sourcing a car that came with an AEB. The ECU system in the drive by cable cars is horrible in comparison to the newer drive by wire cars. The AEB head is a nice upgrade, but everything else about the vehicles that came with them are negatives. Not to mention the only A4’s that came with AEB are pre-facelift (not as good looking).
All the rest looks good Mike.