I've been thinking about two map ideas:
First, I'm talking about objective-oriented maps like you find in Wolfenstein: Enemy Territory and others. I figure it can be done given what we have. To start off, it can't be a siege map because the teams switch and players stay eliminated. A normal CTF could do. The defending team would have to get *one* flag point so if the time runs out they will win. The flag could be blocked after the first point (potentially activated by the flag bearer falling into a trigger). The point needs to be triggered right as soon as possible so the defending team can't end the round as they please (for servers with flagcapsendround 1). The opposing team can perform tasks (and set off triggers) to finally unblock the flag. The flag would earn them 50+ points to win the level.
I am not so sure about multiple spawn points that are removed as objectives are advanced, except short of a func_train unblocking a teleport. The only problem with multiple spawn points is getting the defending team flag to trigger ASAP.
That across, I'm not sure how well it would play with the limitations and the type of gameplay Paintball enjoys, but that's my two cents.
Then, there is the race map. At the end of a long path, there would be a flag that would earn 50+ points to win. So that one team can't get a head start and have no way to lose, there could be camping areas around so that newly spawned players can camp upon those later in the track. =P
And there are my ideas.