Regarding (5), give the option to either take SBD or SP. Just use a discount on the first, or a premium on the second (in other words, invalidate the "Same dollar value" part, through incentives to do the second).
Psychologically speaking, a premium on SP sounds better.
Hm, interesting thought! However, it's a bit hard to contact 50-100 people each week to ask them how they want to be rewarded! :(
There may be some workarounds
Send a message to everyone who has participated (or is pretty active) with the two options
Default to SBD but reduce payout by a %. If you have a price list for services offered, update it to reflect this change. If asked, say you can offer an SP payout with a % boost. You can also put it on the price list (if there is one).
Automate the process of asking through some kind of webform that cleaners have to fill (bullet option on what they want to be paid). Then issue the payments depending what they've filled in the form.
If there are obstacles to any of the above, adjust accordingly to circumvent :P
Hm, yeah a web from with a default action could be a way to do this. I'll put it in internally as an option, thanks! :)