If I were you, I would send an e-mail to Jerome or/and Elon himself explaining the situation. After putting a 40.000$ deposit and waiting 2 more years than originally scheduled, I don't see why they can't put you at the front of the non-sig reservation holders. Maybe they don't want the X-sig queue to shrink 'cause they have no time to find another buyer to take that spot but at least they should give it a try, something like enable the upgrade button for the non-sig and if someone upgrades before it is your time to configure, you get to be at the front of the queue of non-sig reservation holders. Or, in case they don't want to disturb the (force of the:biggrin
queue, just switch spots. If not, then I think it's fair to make you decide between X-sig or end of the line.
If you were not an original X-sig and just upgraded, it's more difficult. I'd lean towards this system: same as before, wait for a non-sig to take your spot. If there's a buyer before having to configure, there are two options. That non-sig has a reservation number lower than your original, then you recover your original spot in the queue. Option two, it is higher, then switch spots. No one interested before configuring, signature model or end of the line.
Is there any loophole I'm missing?? I think it would be the fairest system but criticism is well received. I think the key here is that they want the signature reservation holders to be the most convinced ones so the penalty for stepping back is that high.
The reasons you posted (enough performance of the 90D, better range,...) are sensible and have a point. It's an amazing car, I trust Elon on the unseen features but you should be comfortable on purchasing such an expensive item. The last thing you want for your company is having your most faithful buyers annoyed. I love Tesla but sometimes I don't get this stiffness on the customer service side.