A very good point. I would agree that limiting your potential customer base isn't a good idea from a purely business point of view. Though I suppose if your aims are more along the lines of attempting to create a sim with "ultimate" realism then that might not be of such a concern. Who is to know what the devs ulitmate aim is. Presumably they are in it to make some money at least otherwise it would be entirely free to use.
I can only say if it were my project, (which of course I understand it isn't), then I would work it along the lines you proposed. Keep the aids in, (only to the extent of allowing users to use alternative controllers, not to make driving easy), but give them a distinct disadvantage, though not to the point where people will think it's pointless taking part, (say 0.5 second per lap for each aid used).
In my opinion, ultimately if a project is going to be so exclusive your customer base is practically non existant you might as well have just developed it for you and your mates to play. Which is fine if you're doing it purely as an intellectual exersize (ie to prove that it can be done), but if you're out to make any money out of it then it's not the best business plan.