Seems like a simple solution. I’d happily pay $50 for expansion +1 slot as a vet. A new player gets great value by getting the base + HoT and has 5 empty slots to work with. But let me choose!
Personally, I will get the ultimate because I’ve gotten far more than $50 of value out of the game over the years and I have no problem giving ANet my $. But I think they’d quickly quell the concerns of the masses with the above solution.