Funny, I was just in my Boler
mocking up the very things you're thinking about
I had bought enough ply to make a counter completely across the front, and was originally thinking about making that whole area a desk, then using a chair in the main floor area, so I'd be facing forward with my feet in the "keyhole" (which is where I'd keep the chair when not in use).
Right now I, too, have a counter extension running forward along the driver's side wall next to the kitchen. I was thinking I'd just have that on top of the main desk, with a space between it and the desk which would be handy to slide papers or whatever (as it would be about 4" tall).
But I also like the dinette idea, and I do like to have a place to just set daily things when I come in the door (where the heck else does one toss a backpack, etc.?). Of course these could go on the original bench under the big desk, but...
So today I was mocking up making my desk/table run from the kitchen wall over to where one single seat would be on the door side of the trailer (with a small storage bin on the side wall to make the back shallower and more comfortable as you mentioned). This would give me the "set down a backpack" space (of course that would be MY seat!) by the door. And a place to sit without having a separate chair (although with one of those I could seat two).
I think I may cut my large piece of plywood (28" x width of trailer) so that there is one large "table" piece that runs from the kitchen wall over to where the door side table edge would normally be with a dinette conversion, and then try that out. I can save the door side piece in case I want to make a full width table. Or I could cut the whole thing down to just a "normal" table later. I'll put my current galley extension counter on a couple of 1" x 4" "rails" running perpendicular to the long wall of the trailer, and set it down on top of the desk. So I'll have that small space for papers or whatever to slide in and store.
I'm trying to talk myself out of the radical conversion I keep thinking about, wherein I move the kitchen to the front wall, then make a long bed/settee along the (former) kitchen wall. I like that because I'd have a "permanent" bed/table all in one. (In other words I'd have the table set up very similar to the current rear dinette table if you make it up, but just shifted a tiny bit to the door side for my 32" wide permanent bed/settee).
I really like the permanent bunk/settee/also-where-you-sit-at-the-table set-up -- it's what I'm used to on boats. No "deciding" whether to sit at the table or on the bed (I tend to hang out on the bed all the time and just use my galley extension that runs off the sink side and over the foot of the bed for my table, but that's not so comfortable as no place to lean back).
That's a lot of work though, so I'm going to try the dinette ideas first