I test fit the Audi wheels and design-wise they are spot on. The pepperpot look works well with the car's shape.
Ideally there would be a little bit of suspension drop as the wheel gap will be pronounced, especially in the rear, but the wheel offset is correct and there is no tire sidewall rub onto any suspension components.
When fitting the wheels, I had to pay attention to the lug nuts. Regular lug nuts are not recommended to be used on other than steel wheels, but even trying them on was problematic. The Audi A3 uses wheel bolts instead, with a ball shape as seen from the wheel as well.
Luckily I found ball-shaped lug nuts in correct size from my parts stash, as
@Lastsoul suggested the ones left from the Miata BBS should work..
Now I just need four more of them, for 5x100 instead of 4x100.
To reiterate, the choice to run the 195/50R15 tires comes from experience in the earlier rallies. While I could just suck it up and run the stock steelies and 185/65R14 tires, they would just get chewed up on the harsh tarmac on the Baltic stages. Now I can just use up the Federals while they are still decent and have good summer tires for use outside the rally event. If the suspension is lowered, it would have to be such a modest drop that it would not hinder the use of stock tires.