Test drive done. It ain't perfect, but I like a lot. Some details:
The car has 105'000 km on it. Engine was swapped at 93'500 (reasons unknown, promised to find out from the previous owner who's apparently a friend of the dealership's owner), the "new" one had 62'000 on it when swapped, so ~74'000 on the engine now. T?V was done in March at 103'500 ("keine M?ngel"), good until 2019.
Gearbox is the 5-speed manual. Like it a lot, really short and precise shifts, smooth, no issues in any gear that I could identify. Clutch engages really early, feels a bit weird since the "pressure point" is really hard to feel (much more distinct in most other manuals I've ever driven), but I got used to it rather quick. It could definitely use a 6th gear for Autobahn cruising, but that's not the point of the car anyway.
Brakes are fine. Tires are bad - different pairs on front and rear, rears are fine-ish (enough profile, though quite old), fronts are hopeless - from '07 and nearly bald. Dealer will throw in a new front pair. Also no winter tires/wheels (has apparently never been driven in the winter), will have to get some.
Soft top seems good. Car was parked outside at the dealership for a while now, with heavy rain in the last couple weeks, I couldn't detect any leakage. No tearing anywhere, straps on the back of the roof look like new, seals are good. It needs a thorough cleaning though, there is even some light mold on the inside - dealer said he'll get it done at part of pre-sale service. And - not sure how normal this is, but it's bloody impossible to raise the roof from the inside. It's quite heavy and the angle feels like I'm going to dislocate my shoulder before it lifts up. I couldn't do it in several attempts, resorted to quickly hopping out and grabbing it from the outside.
Wear and tear seems alright. No rust that I could see anywhere (looked in the wheel wells, door wells, under the liner in the trunk, and as far as I could see inside the engine bay). Tiny dents on both front wheel arches, a scratch on the right mirror (it also only moves vertical, lateral adjustment is broken), and some scratches on the outside radius of the wheels. Interior is really good, leather seats are in better shape then the ones in my A5 (at 70kkm), no major scratches, nothing broken. Electrics all work, once we got it jump-started - the battery was dead from sitting in the lot; will get a new one before delivery, too. Only the DSC lamp stayed on throughout the drive - dealer said it's probably also due to battery, should be fixed as part of pre-sale inspection if anything's wrong there in any case.
Drives great. Idled a little rough at first but was fine once warmed up properly (might have also been the ECU reset thing due to dead battery). No unwanted noises or anything unexpected. Loud above ~120 km/h, but that's the soft top, nothing to be done there I guess

Again, it's not a car for long autobahn cruises.
Got the price down to 8800 + new pair of front tires, new battery, a full pre-sale inspection including a thorough cleaning of the soft top, and a 12 months used car warranty (covers any work on mechanical or electrical parts + 40% of parts prices).
I'll try to find a few more to look at, don't like choosing from a single option. But I like it a lot, and would probably take this one if all works out with selling the A5 as planned. Any input on what I might have missed or should look at again before committing?