Does anyone who's been in this game a longer time than me know if Sami has considered a re-engine option for things like C440 and DC8? Both received commercially very viable upgrades (turboprop and turbofan) during their lives. Cant put is as a request feature as that forum has been closed for two years!
It has been proposed and it was shot down. (https://www.airwaysim.com/forum/index.php/topic,18916.0.html)
The conclusion of that thread was that the number of airplane types that historically received engine upgrades is too small to justify implementing them over other higher priority features.