I do agree that dropins shouldn't have RP. But I do not agree that dropins should be solo queue only... that does not help the community or game develop.
If club were the only place to take a pre-made group of friends, how are we supposed to find these friends and know they are capable players if we are only searching by ourselves in dropins? I may meet 1 or 2 ppl as teammates in a solo queue dropin, in your scenario, but we cannot play together again until we have a full club? That seems silly and would hinder groups growing and branching out.
You need dropin mode nearly as it is, aside from the unnecessary RP.