Well something "fishy" there.
The problem that you can't upgrade the "default" ship designs , especially the problem "visible" with scouts , colonization ships and transports.
Let's say I developed new engines and want to upgrade - system does not let me to save
The bigger problem is (if we leave aside that I can't change/save standard design) that because this default/standard ship types sometimes is "more advanced" then technologies I have , for example I don't have medium hull type so I can't create "paralel" design with new engines.
I think we have 2 problems here - one logical , I believe it should be resolved in MoO1 style by allowing the race to have ONLY she ships it has technologies for, so basicly we should start with no sips.
But if we start as in MoO in "later age" then we will have more tech to start with and this means if we have colony ships we (and all AI oponents) should have all the technologies requered to build colony ships.
The other problem I believe is leftover of GalCiv1 engine, I think ship types saveing aproach should be changed to allow the "standard types" names to be used/saved this means standard types should act not as ship types but as templates to create such.