I voted yes, but game needs some more "optimise features", like multicore support. I am sure most of the players have more than one core, so increasing in-track slots wouldn't be that good for clients.
About server you will just need a bigger upload connection. More slots, more cash, better PC. Isn't it obvious?
Also there is no need to have every single server with maximum slots(both spectators and in-track); its your choice. That's why you shouldn't say "It will be more expensive" and bla bla bla. Of course it will. If you don't want it, you can stay on 47 and 32(i hope the numbers were correct, i am not sure).
+1!