Here - this is untested, but should work... added a new CVar (sm_suicideintercept_time defaulted to 0) where you can set the number of seconds to allow players to use suicide commands after spawn.
You'll need to compile it yourself with all of the required includes since I'm not home and don't have access to my server - I only edited the sourcecode while sitting here in my hotel room...
Let me know if there are any issues. Hopefully you have a test server
Once I get back home, I'll test the plugin and officially release it.
...:: TnT Edit ::...
Oh, turn off auto update for this plugin while using this unofficial release.
Actually, I just uploaded a version that doesn't use updater - go to
http://www.sourcemodplugins.org/pages/smwebide/ and upload the .sp file there and it will compile it for you.