I would say it will have a big impact on your resale value when you come to sell it,people tend to want standard or slightly modded cars which you could return to standard.
Once you have welded in plates they would be nearly impossible to remove.
Then again if you want it for safety its a different matter......
I mean by the time I sell it, it probably wont be worth that much anyways. especially if the prices keep dropping like they are now. Hopefully it will level out soon (for the guys who plan on selling theres in the near future.)
Anyways, I want the cage for safety reasons which is why I dont want a show cage. (obviously)!
The thing is with bolting in the cage, it can be removed and only the welded plates would be left which can be hidden from view under the carpet, if for some reason I wanted to remove it.
The cage im looking at is a Safety Devices (Rear)cage from Mark Fish. The rear seats can still be used if needed and it has a removable harness bar. It looks a v good piece of kit.
I have a Saftey Devices bolt in cage in the rally car. They use good steel and are well made. It saved me once, stood up nicely and I was able to use it again when I reshelled the car. They have had their 'financial challenges' over the years and now manufacturing is done in Poland/Eastern Europe...
Tony Fall was a pretty handy driver in his day. Good brand. You won't go wrong.
The set up you've got sounds fine should you wish to ever remove it, plates will sit under the carpet etc. You can also still use the rear seats. It will also give the car more torsional ridgidity and basic protection in a light roll on a track.
Only thing is that if Mark fits it he'll need to remove all your rear trim (or most of it) as he'll seam weld the plates in and you wouldn't want hot sparks burning holes in your seats, carpet and trim. Then trim will go back in around it. In my experience it never goes back in quite the same as it sat originally!
I'm sure he'll cover the Recaro's in suitable protective material, but a welding spark takes no prisoners.