I'm impressed TB has asked this question. I love the open mind attitude. I also like the challenge, and will think about it over the next couple weeks as I have time...
I was about to press "post" and a couple very high-level thoughts just came to mind:
1) Think "Transformers". Couches and loungers that turn into tables and bars. Somewhere I saw a boat where the rear lounger morphed into a picnic looking table (one table, with a couple benches on each side). When it folded up, it became a double wide lounger in the center of the rear of the boat. I wish I could remember where I saw that... But I think that sort of thing is the next "new wave" in pontoons. Everything else has "been done".
2) Along the lines of the above, think "Legos". I'm thinking modular seating. I like the lounger concept, but sometimes I like how the SLi looks with the sundeck. Right now, I can't have both, but would like to. So, if you had SOME limited amount of modularity to the boat, maybe the owner could purchase different pieces of furniture and use what you want when you want it. Whatever piece of furniture you didn't want to use would just stay in the garage. One week, you might use the sundeck. Next week, the lounger. Most of the boat's furniture would have to stay fixed, obviously, but maybe SOME pieces could be moved around and the OWNER could sort of design his own boat (or more like change the layout from time to time). Such as removing one lounger, and replacing it with a small bar table with two seats facing each other. Pieces would have to be somewhat quick release, but some amount of "nuts and bolts" to keep things safe would be just fine. You wouldn't change it often so much as you'd be ABLE to when you wanted. This might be something you change only a couple times a season, depending on the crowd you were entertaining (such as a bunch of kids one time and a bunch of adults another time). I'm babbling, but maybe it will trigger some thoughts.
Here another thought. There's been a lot of talk on this board lately about the split loungers with the center walk-through vs the single double-wide lounger of the SSL. What if you made a system where you could have both? What I'm getting at is you could have the split loungers, but make it so one of them could slide over to the other to turn it into a double-wide like the SSL. They could be slid together for the wife and kids (or couples) to snuggle. And slide back apart for the guys to use...
How to get a poker table on my boat has been something I've been thinking off and on about for a while. I've not come up with much other than a miniature hold-em style table, just big enough to hold the community cards. The players would have to hold their own cards, but the 5 community cards would go on the table. Some kind of chip-less chip system would be needed. Can't have stacks of chips on a boat (that moves). My thoughts have gone from a high-tech electronic chip scoring system (not likely something I could make) to a simple white board (also a "not", but something in the middle has got to work, I've just not come up with it yet). Anyway, a poker table is probably not the kind of idea you were looking for here, just thought I'd mention it as something I've been thinking about. Maybe you might be interested in it. Hold-em is VERY popular... It would make for a great "guy" outing.
This one's also a bit "out there" (like the poker table idea) but kids love slides. Maybe an optional piece of furniture might be a slide? Detachable? Wouldn't have to be huge, just something for them to play on. Matter of fact, take that a step further and imagine a water park on a pontoon boat. We bought our boat largely for our kids, but there's not much "kid stuff" on ANY pontoon boats I've seen. Sure, there's pulling tubes and stuff like that, but there's nothing "cool" to a little kid on the boat anywhere. Not sure where I'm going with this, but water parks are HUGE money. They're a ton of fun. Kids love them. So do parents. A pontoon boat is on the water, so you're halfway there just being on the water. The thing is NO ONE SELLS A KID FRIENDLY BOAT. "Friendly" isn't the right word. Maybe I should have said "kid-like". Something along those lines would certainly be unique, possibly enough so to sell...
I have to go, but I'll keep thinking. What you should do (and what I plan to do) is think of different things you like to do, and see if you can merge whatever that is with pontooning. You might come up with something "shattering"... Ha Ha.