I have my own ways of stopping spawnkilling
1. Make a door only openable from the inside, other team members wont be able to enter.
2. give people atleast 5 seconds of invincibility.
3. if you dont do 1 then atleast form a invisable forcefield around the spawnroom that is only openable from a button in the inside and will close in 2.8 seconds
4. form the spawns Far apart so if theres a certain class, they will spawn in that area or if its no classes and just kill, SCATTER THE SPAWNS OVER A LARGE ARE BASE.
5. Create a field mean't to KILL enemy members who tend to camp NEAR the base.
6. force defences to be setup by the time the build or "Bases" Load. this could be acomplished by create zombie or vehicle spawns with a bot or "sentry" mean't to kill others on the enemy team. it may be buggy but its possible, I've done it. Yes this requires botevents.
7. Place traps around the base mean't only to kill others on the enemy team. This can be done with invisable paint in certain colorsets or checking off the Option in events. the trap could include the following: Bullets, Bombs, instant respawn, Death, What?, Caaaaaaake.