I like your idea, but I agree that on big servers it would take even longer to respawn. It would seem like forever, at the end of a fevered game. I had another idea regarding SD, tell me what you think of this:
If the total elapsed time were over one hour, and it was SD, and had been SD for at least ten minutes, the second extendtime/reducetime vote would initiate a PowerUpGrade mode. During this phase, destroyed enemy structures would convey benefits to the first player to grab a token or icon. Aliens would get PowerUps, Humans would get UpGrades. The PowerUps would be like Strength, Speed and Endurance (Alien hormones kicking in from evolutionary programming). The UpGrades would be weapon modifiers or health or armor boosts (Human reverse-engineering of Alien technology, via nanites or cybersymbiotic enhancement - becoming the enemy). "Let he who would fight monsters beware, lest he become one."
PowerUpGrades
Human Structures: Turrets, Teslas, Telenodes
Alien PowerUps: Strength, Speed, Endurance
Alien Structures: Acid Tube, Barricade, Eggs
Human UpGrades: loadout based
see here for some ideas:
http://tremulous.net/phpBB2/viewtopic.php?t=4036(By my second post the idea had coalesced. Risujyn also offered a very incisive critique - thankfully, by PM. I've made some changes, notably the Alien PowerUps, and not having glowing balls of light for the icons or tokens.)
also, now I'd say lose the icon or token
banners announce who got what PowerUp or UpGrade
first player who runs over destroyed structure gets PowerUp or UpGrade
(yes, through acid splash and turret slag)
Humans can't use PowerUps (only affect melee attacks)
Aliens can't use UpGrades (only affect equipment/ordnance)
SD play-modifier only
alternative to timelimit, endless votecalls, Rampage (I've got nothing against Rampage, I just like variety)