I think the ROI you are talking about is used in Minnowbooster and in bid bots it is used only for bids of vote buyers but not for delegators. In bid bots we sell votes through bids then daily payouts rewards are distributed in delegators according to their delegated SP share. Different bot owners get different percentage share for their services mostly get 20% or 15% and give back remaining rewards to delegators while we get only 3% and remaining 97% is distributed to delegators. In bid bots you don't have to delegate/undelegate or renew your delegated SP every week because it is permanent way to earn regular income.
Yeah, I think bid bots are most profitable for delegators if they get maximum percentage share of daily rewards like we are giving 97%.