Quoted from Frax:Timer for completion after first standup switch hit in that area then kill the power to the slings. Done.
This was also going to be my suggestion. On the Data East Royal Rumble, they incorporated "life bars" on the wrestlers showing on the DMD and as you hit pop bumpers and specific targets, it would lower their energy levels, etc... a similar function could be employed here either with a timer as you mentioned, or a "damage meter". Since they mention the top kick out hole is how you count the pinfall, and it only counts to 3 if you've done enough damage, maybe after the 3 count the slings power off and the ball drains to the lower playfield.
Definitely a lot of options to make it fun and follow the theme, but all code dependent.
This might be wishful thinking, but with the new SPIKE system -- I wonder how long before people figure out how to modify and write their own code and rules? Would be pretty awesome for home brew folks to be able to implement their own set of code.