Sometimes an hour for the map isn't enough and you want to keep playing the map so this will help. For hard server only, because most of the time there is going to be just you, and if there are other players that want to extend the map they can also vote for it. That and more people complete easy than hard maps, with it being on easy people not might like playing the same map for an hour compared to the normal 30 minutes. people might leave because they don't want to play the map again
There's plenty of difficult maps on there like 666 that I'd expect to take a long time, I'm not opposed to an extender limited to Hard, but see what Teddi thinks.
In a way there is a votemap extension already in place; albeit not in an intentional way. If no one votes for a map at the votemap period it'll reload the map you're currently on. I know this isn't ideal regarding position for staged maps; however it's a current working solution. I'm not sure about allowing for a solo extension (or extensions at all). If the server is < x (3?) players it could be something worth doing but the difficult aspect of it is what is too many players if we were to do this.
It doesn't do this all the time, I've only had this happen twice, while there are many times where I didn't know what to vote for and so there was no vote and it picked a completely random map.
In which case to add more consistent behaviour I'll add an extend feature of sorts. I'm not quite sure how this will actually take shape; given that the actual countdown aspect is precalculated (and everything else discarded afterwards) for the countdown on Surf. It might be as simple as a /voteextend or it may appear in a different way. It's possible the command may also end up gated behind some sort of requirement or restriction as to prevent abuse (e.g. triggering the rtv cooldown).