make it less fruitless
I noticed that if you join a combat game late, even if only a minute or two, that you really can't get into the swing of things because you are too weak compared to the other players.
Perhaps what could be done is that a person joining is given a level equivalent to that of the LOWEST team member on that team. So if joe-alien is the lowest with level 2.2 then a person who joins at that point would have that same level. (they would not get any kills or death credits though - just the level credit so they can get upgrades)
To pevent AFKs from impacting this, the levels of those who have NOT had a kill or a death would not count in the above.
In this way a person can join a combat game in progress and know that they won't have to suffer though a pointless game because they are too weak to do any damage. (it could be made into a switch that is server defined) By using the credit of the person with the LOWEST score you assure that late joiners won't be overpowered, but that they at least get a little something.