I gotta go with Tesco on this one.
I'm not sure there is much that can be done. The PBW game is posted with time paramneters and any additional requirements in the notes. I don't think anyone should be scrutinized out of the corner of one's eyes just 'cause they are perpetually the Last to upload (but do so within the stated requirements).
I, too, sometimes look at a game where I am excited about getting my turn back to see how I did and (briefly) let some thoughts run through my mind about the (single) player holding the game up. But I remind myself that everyone doesn't allocate the time and passion I do to the game and that they have other hobbies or RL events to spend time on.
I haven't started a new game on PBW lately ('cause I'm in enough at the moment), but I like the simple: "36-hour T/A; miss 3 turns during the game without requesting "permission" and you're automatically booted."
And, as always, there is the player who loses interest 'cause he is losing (pardon the pun

). He'll likely drop which makes the game unfair as the people next to him gobble his territory up or his allies begin to suffer. I don't believe in this. I play till the finish (or until my team agrees to "throw in the towel")...but not everyone feels this way.
And, assuming it's possible, I'd hate to see some kind of award system for people who submit more promptly than others that results in direct game benefits. I'd hate to see my position in a game suffer for reasons that really have nothing to do with game play ability.
I once posted a poll on what makes games interesting. Fast turnaround, 6 players, game sponsored by a "heavyweight", and (already) knowing the people in the game were the winning items. I'd have to say, now that I have been on the forum a while and tucked a few PBW games under my belt, I can understand why the poll came out the way it did. I know right now of many people who I would like to play with who submit turns well within the time limits, won't quit, and offer good play.