Everything can be fixed without overthinking it. I’ve been welding and repairing things like this for a long time. Just get over the intimidation factor and do it.I wouldn't discount it so quickly. I'm not a welder, but from the little I've read, it's not a simple process to weld aluminum correctly. It differs considerably from welding steel. A large part of doing it successfully seems to come down to understanding the chemistry of the alloys, and one aluminum isn't necessarily the same as the next. The process used by the welder really needs to be informed by the alloy "fillers" that are incorporated into that particular aluminum, not to mention whether heat treatment has been done. I recall the forum having this discussion a few times, and part of the missing ingredient here is that Audi isn't sharing (or hasn't in the past) this information. From Howie's thread on this (quite a long time ago), I seem to recall we couldn't locate any markings or information on the braces, themselves, and we certainly don't have any aluminum prep insights from the factory for the frame.
Can you weaken the area you're actually trying to reinforce? Again, I'm not a welder, but the info I've read suggests it's a real risk.
Some info on aluminum vs. steel welding and the risks, including tensile strength:
Some discussion around welding T6 aluminum and the ability to cut tensile strength as a result:
Some more discussion around aluminum car frame welding - plenty of comments around risking tensile strength:
What I've taken away from much of what I've read is that:
(a) Aluminum welding is much, much harder to do properly than steel.
(b) If the welder doesn't have specific information on the alloy chemistry, it's impossible to choose the correct "filler" materials for that aluminum.
(c) If the aluminum was heat treated (part of getting something like T6 designation), it will lose a significant portion of its tensile strength if welded after the fact. The only way to recover this afterwards appears to be re-heat-treating the metal.
Given how much forum owners love their R8s, I think the natural inclination would be to go reinforce the frames with these plates. But as I said above, historically Audi doesn't seem to have sanctioned shops doing this. Why? Maybe that policy has changed? It would be interesting to get some data points from folks making local inquiries. There was a forum member (in Michigan?) who recently had a number of shops turn him away for this job, as well, citing lack of support from Audi. I guess all I'm saying is that it appears more info/research might be warranted here.