I have mixed opinions on this myself since I am learning to love PHP but Brad had a good suggestion earlier about being able to create .cgi pages from within the CP and it seems to me that this would also allow us to use the styles and variables and of course recent visitors etc. I realize that this would increase the overall resources used but if a person is surfing through the external .cgi then they won't be on the summary or forum pages at the same time so it will still be single sessions.
I think the thing I would like the most as far as appearance and ease of design change would be to have the $TBT and $TBB available. Allen has done this with hiw PHP styles hack.