We found ourselves in a similar situation as well. We chose our new Gateway 3713CK because of the floorplan. The difference between it and a "normal" mid-bunkhouse was what really made my wife fall in love with it. However, the GVRW is 15,500 and after the options we added from the factory (double pane windows, awning toppers, generator prep) it left us with a CCC of 1196 lbs. Then on the way home I also picked up an Onan 6500 to put in there. So I'm already down to 896 of CCC.
Since we will be traveling extensively with 3 kids for the next several years, I already planned on immediately putting on the MORryde Independent Suspension and disc brakes when I drove to pick it up in Michigan. While at MORryde, I asked about the feasibility of upgrading to their 8K suspension given how little CCC was left and they felt it wouldn't be too harsh on the ride to do the 8K suspension with their lightest rated springs. I know this doesn't legally give me any additional CCC, but with that suspension/brakes and the new Sailun tires, I'm pretty confident that even if I'm over 15,500 some that things will be alright. The MORryde IS is definitely a beast which alone probably added 3 or 400 pounds to the weight of the coach. The weak link now would be the frame, but since Gateways are now built on the Cyclone line, maybe the frames are as strong as them? I don't know, but I also don't plan on seeing exactly how much I can overload it.
I know it isn't ideal, but there really aren't as many full-time coach options for families unless you go with a toy hauler . Most are just oriented towards couples.