Current options on multipurpose lifters?

A flat tappet cam will always be a flat tappet cam and a roller cam will always be a roller cam. You cannot mix the two because the design of the lobes on the cam are very different and they will self destruct if you play mix and match. Your choices seem to be, #1- do nothing and ignore the start-up noise, or #2- replace all the lifters with new ones.