The possibility to convert aircraft already exists, but one thing I don't understand is why it isn't possible to convert aircraft to a different MTOW or a different engine available for that production model yet? I'm talking about the possibility to convert a 737-200 to a 737-200Adv, or to convert a 727-100 or 200 Adv to a different MTOW, or to install Pratt and Whitney engines on a 767 that came originally with a CF6 engine, for example.
The reason for that is that conversions like this are very common in real life, according to some research I've been done (like
this one and
this one). Other reason is that the modern eras of the game are plagued with models with tens of MTOW variants and engines, which makes it so difficult to pick models from the Used Market that share the same specs that many players may give up and opt to order new. I think if convertions like this were possible, we would see smaller order backlogs!