Be careful what you ask for. You might be taking away that which makes an a-frame special.
Each 2ft of additional box length adds the following:
14 sq ft of interior space (14% increase over 14ft box)
1.5 ft of length to each roof panel (23% more weight per panel)
1 ft to raised height
More flex in all body parts unless strengthening and resulting weight i9 added.
Many will not buy an a-frame that won't fit in the garage, and the roof is even more difficult to raise.
There are 3 longer campers with 14 ft boxes. Rockwood 212, 213,& HWs. We have the 214 that has full queen bed, small dinette turns into twin bed, and hard shower/toilet, with dormer. More outter storage, and dry weight is 2700 roughly. Pulls wonderfully.
We sold and bought a house this summer. All newer construction in Colorado with attached garages had 19-21ft bays standard (our previous house). Folks with long trucks measure carefully because they won't fit in many standard garages. There are newer standard homes and semi-custom homes where people paid for extra-long garages (22-24ft bays). Our present house has the extra-long bays, and I love it.
The 14ft box a-frames are 20ft 10in long. A 16ft box (what the OP is asking for) would be almost 23ft long, and will not fit in most garages.
My A122 is just 17ft long, so I can put camper plus mower and lawn and garden stuff in the same bay. And my present garage is high and long enough to set up the A122 inside and still clear the garage opener track.
I still believe that going to a 16ft box is going to lose some of the features that make the a-frame so special to us. If we had wanted the extra floor space, we would have bought a canvas side PUP. OTOH, the fast and easy setup compared to the PUP made the A-frame the more desirable choice.
let your camping style determine your equipment
2014 Rockwood A122 a-frame
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time
We have the newest Rockwood 214HW that is considered to be 21 ft long bumper to tongue. Our garage barely fits our 2014 Ford F-150. The garage is just at 20 feet long. We pay for storage for our trailer, and it's worth it. When we open it up in the storage this particular A-Frame with its length is higher when opened. (Approx 10 feet high ground to peak). We found that having 2 more feet of living space is much nicer.