I am not sure this will really help.
By giving a percentage of the coins based on the damage done to the bounty, all you are doing is replacing one number with another (much smaller) number.
For example: if you have someone in the alliance at the top with say 5billion damage, that same person will still be at the top with say 30k coins.
Not really achieving anything other than making it a smaller number.
The concept of additional stats, is interesting and would be nice to see. But again, still wont change anything. You will just see them with more attacks.
Some alliances do adopt a policy of “If you start a bounty, you are responsible for that bounty being finished”. Obviously with an option to call out for help if you run out of guys to throw at it.
Alternatively something akin to a buddy system. You run in pairs of hitters and cleaners.
Just my 2cents worth.