It would appear that I arrived at the same conclusion as the OP at the same time. Jinx!
https://forums.frontier.co.uk/showt...irements-met?p=6874318&viewfull=1#post6874318
One explanation given against accepting missions without meeting the requirements other than rep is that it can adversely affect BGS and presumably PP. That may or may not be true, so perhaps "reserving" a mission before commencement could be balanced by much higher penalties for failure? I'd be quite happy if, say, I accept a VIP passenger mission, fail to deliver, and not only lose a great deal of rep and fines from a faction, but for them to also send the bailiffs after me to collect.
Preparation is what it is all about of course, and some missions will be beyond the player's capabilities. The decision to accept those missions is entirely for them to make. Not everyone has a multipurpose vessel that is capable of meeting the requirements immediately, but many of us have worked towards having the means in some form to be able to quickly react to opportunistic mission offers if they were allowed.
Regardless, as an observant, relative newcomer to this iteration of Elite, this mission mechanism sticks out like a sore thumb when compared to Wing supply missions that allow the player to accept them in an otherwise unsuitable craft. It should be left to the player to decide whether they have the resources to fulfil
any contract within the time frame, and to suffer the consequences of not delivering on the promise.
Risk/reward left in the agency of the player.