All of this can be done if the players wanted to, as servers in ETF2L are managed by players not admins.
Say you're 4-0 down with 5 minutes left - Yes it's still technically possible to win but you as a team decide it is not and want to move onto the next map. You can say "Good game enemy team, we concede" then type "rcon mp_timelimit 1" and the match will end - Take your screenshots and logs will be correct. Add a little explanation to the matchpage if necessary..
This concept of Dead time only exists because players don't think about ending prematurely during games, only people watching do. If you prompted people to do it, they would.
A "GG" button would be cool too but then again, I can forsee people misusing it and causing drama - I don't know about ESEA btw, no opinion on it.