I really like the way you look at the problem it does give us food for thought. We think that a complete custom job will also be very expensive.
The idea was that the (new) design would have a few changes like removing the see through windows and the skylight over the vestilube with its huge cover which we never use.
But at the price of around 300euros we think it would be cheaper to buy the new tent and have someone remove them. It would still be cheaper than dishing out for a complete rebuild.
Thanks Peter... you've given us a different way of looking at this problem.