I was just about to request this as -70 conversions have just popped up in GW1 and I have hit this problem. At least one can save the 80 days for the first D-Check by immediately cancelling the check after taking the a/c out of storage, but it's still a HUGE waste of money.
A similar problem occurs when buying an older a/c off the used market for conversion. One has to wait two weeks for delivery before sending the a/c off for again conversion. Can conversion also form part of the "Additional Maintenance" box on the Purchase Aircraft page? This also brings up the question - should we re-allow aircraft with expired D-Checks to be on the used market? There must be many a/c ripe for conversion that the owner is currently unable to list.
EDIT: another problem I just noticed with conversion: The seating configuration is reverted to default on conversion! I can kind of see the mechanics of why this happens (it becomes a new type and you may not have the correct seating plan set up) but... it just means yet another delay sending the newly converted aircraft off to be reconfigured as it was originally. So maybe "Convert Aircraft" needs to have an option to select a seating plan. For a simple conversion that doesn't change the a/c "size" such as DC-8-61 to DC-8-71, there could be a tick-box to leave the seating configuration unchanged. For one which does, such as a combi-conversion, there needs to be an option define a configuration, like there when purchasing from the new or used market.