My thoughts:
* committee should be able to set a global lower limit, E.G. 6 BTS
* committee should be able to set a global upper limit, E.G. 300 BTS
* committee should be able to set a global percentage, E.G. 1%
* issuer (or committee for BTS and committee issued smart coins) be able to set the per-asset fee mode, E.G. flat mode or percentage mode
* since issuer doesn't get any split of fees, to avoid harm to other parties, issuer has no permission to set per-asset based parameters
More flexible settings would be:
* issuer get some fee split (discussed below)
* issuer be able to set a per-asset lower limit
* * if it's lower than the global lower limit, issuer pay the difference from fee pool to network
* * if it's higher than the global lower limit, the difference pays to the issuer
* issuer be able to set the per-asset percentage
* * if it's higher than the global percentage, the difference pays to the issuer
* * if it's lower than the global percentage, issuer pay the difference from fee pool to network (not to the referral program, to avoid referrers earn quick money from issuers by self-transferring)
* issuer be able to set a per-asset upper limit
* * if it's higher than the global upper limit, the difference pays to the issuer
* * if it's lower than the global upper limit, issuer pay the difference to network (not to the referral program, to avoid referrers earn quick money from issuers by self-transferring)
In this way issuers are motivated, referrers may loss some if issuers set low percentage and/or low upper limit (while issuers also need to pay some in this case).