I know how you feel - I have had company cars and questioned why I have owned my Porsches in the past... I get annoyed (typical Virgo) that it isn't perfect and have started down the road of spending all of my income on making it perfect. At that point I probably won't want it to leave the garage!!
I've always maintained that there are two kinds of cars: cars for getting from A to B and cars for enjoying. Cars for getting from A to B you will park in a supermarket, multi-storey etc and they *will* get dinged and scratched. They will also get stone chips, get wet, do a lot of mileage and will usually not look their best - it's a tool, not a piece of art. Cars for enjoying however you can keep safer by minimising car parks, only driving in good weather and washing frequently.
It sounds like your 993 is a lovely car, so you certainly don't want to use it as an A to B car. Would you be happy with a slightly rough 996 C2S though? Tough one.
Would it perhaps be better getting a small Japanese car to replace the Alfa? Something really rubbish that would contrast with the 993, but would be ultra-reliable keeping insurance, tax and fuel costs minimal? Plus something like a Nissan Micra really would illustrate how good the Porsche is!!! It sounds like you've spent such a lot of effort on the 993 that you should be able to enjoy it for a couple of years on those great days. A modern Porsche that you pile miles on and has less-than-perfect appearance might just spoil the premium car ownership experience for you.
Hopefully that's vaguely helpful!? On aggregate I'd say don't do it!! I sold my concourse condition 944 and bitterly regretted it. Now I've got another £10k and at least a year to get my 3.2 up to my standard.
Good luck!