I think this should be allowed. Maybe once clicked on a stage that hasnt been reached a mini screen pops up saying "You have not made it to this stage yet, thus your time will stop and cubes will not be earned until completion to this stage." Theres been times people complain they cant beat a stage but just wanna see the rest of the map.
Basically !skip then - it's been discussed before, if I recall right Teddi raises that it ultimately allows a player to progress beyond their ability, and it could put them off Surf as a whole and lose the player. If they can't get past i.e. stage 2/8 then that's where they should be until they improve. I think it also takes away the sense of accomplishment when you finally progress if you can just skip to any stage whenever. If players want to see the map they can always /spec someone speed running. I'm not totally opposed to it but I think it has potential issues that would need addressing first.