One idea that is being considered is that the person would need to pay the signup cost to register the new member in order to get rewards from them

I think this is an interesting idea but to incentivize big influencers to advertise to their audience its not going to cut it. It's still better than no affiliate program at all though

edit: Actually from an investment point of view it could make sense if it turns out profitable. Say you refer 100 random people for $1000, you might get your $1000 back from referal fee pretty quickly. Also it encourages advertiser to target the right audience so they have better chance of getting a return.
This would also ease up registration process, so overall i think its a very good idea