Upgauging Aircraft on Order

[TheGrew]

Apologies if this has been requested before, I tried to search and couldn't find anything conclusive.

My suggestion is the ability to upgauge aircraft currently on order. This would be limited to within family, for example A320 -> A321 or 787-8 -> 787-9.
This is a common practice that airlines do with their orders, for example Easyjet converting some A320s to A321s. I have found myself in airline generations wanting to be able to do this due to several late-game bankruptcies and some demand growth my mix of A320 series aircraft could be rejigged to better cover the demand.
I would propose the following restrictions to limit any abuse:
- When an aircraft is upgauged the price quoted for the new aircraft type should be the list price without any discounts.
- Changes can only be made up to 3 months before delivery.
- If aircraft are downgauged eg A321->A320 no money will be refunded.