Hot tub / jaccuzi's a good gimmic as a lot of gossipping or bonding tends to happen there.
New housemates in my opinion doesn't have the desired effect and for me has spoiled viewing as the initial group's bond is what really sets the precedent and the tone of what's to come.
Would like to see a 2 house BB as well. An idea that worked for another BB variant called "two worlds" where on one side of the moat was the house of luxury with all kinds of pamperings and on the other side, over the bridge, was the house of poverty with hard basics only. Everyone starts off in the proverty side and on each nomination the public decides who wins a 24 hour stay in the house of luxury. They're not allowed to steal things across back to the poverty side.
Cornchips' point 7 has a good twist on noms... BB should announce who goes up for the public vote and the others with nominations (but not up for the vote) get privileges, but without any further explanation as to why they've chosen those people. Those without any votes at all that week should be restricted or have a forfeit. Possibly those up for the public vote get asked privately by BB to choose from numbers 1-5 (if 5 people escaped nomination) then choose from a,b,c,d as a forfeit/restriction. The vote person won't know what he's being asked to choose & who for & the escapee won't know that a fellow hm has chosen his/her fate for them for the week.