Hey Oldman!
It's just my few toughts.
Ad 1. The problem is that a grenade (or any other heavy weapon) thrown at a spawn can kill several players or not the one that was intended. Light weapoms as an answer for attacking spawner are allowed.
Ad 2. Maybe it's worth considering, but...
Ad 3 and Ad 4. ...but kick IS "the ultima ratio". Believe me or not. We don't kick people out of the server for any reason or just because we can. Sometimes at full server it's like pure chaos. Nobody pays attention to the requests or warnings of admins (as you have admitted yourself) and giving !warn or even pm to exact player x times in a row doesn't change anything. Of course we have some other useful commands like freeze or gib, but I have personally seen many times that a frozen player just asked why his mouse or keyboard is not working, reconnected and still spawnkilling. So, again, !kick IS the final solution giving us a chance to draw players attention. And in my opinion it should stay exactly as it is now because of it's "ultima ratio".
We, as a TM community trying to make our servers friendly to everyone - from new players, to experienced ones. Sometimes our decisions / actions may seem unpopular or harmful, but we really try our best. It's just hard to please everyone. And honestly, we have a very few main rules to follow...
Ad 5. Whoever was banned permanently - deserved it. Temporary ban is considered as a second (and probably not last) chance to rethink self behavior.
P.S. It' s funny how different things look, depending on where you sit, right?