I've asked around many ppl at Argo about what they think about per-party-member bonus and mostly everyone was happy with that.
This particular bonus encourages veterans to play with newbies and is the main reason why number of LFM's are doubled during those weekends.
I'd like to officially ask SSG what they think about introducing static bonus per party member at some low level (like 1-2%) and just keep 5%/10% for special weekends only.