Main reason to avoid triggering automatic C or D check on arrival of the aircraft or removal from UM listing.
Also, allow placing aircraft on UM with expired C/D checks and / or leave it UM after C / D check expires.
Both options will make it possible to buy and sell aircraft intended for conversions (to combi or cargo).
Also, seller will not have to pay for performing of C/D checks just to maintain the availability of aircraft to be for sale.
I wouldn't mind a "convert to (combi/freighter/etc) at next D-check" option as well
The system was once changed to only allow planes with valid C/D to be listed at the used market, so we'll keep that part the way it is currently.