There are a few options. As you correctly noted, maintaining the slope is key. Technically, I think drain pipes are supposed to either go straight down, or slope between 1/8" and 1/4" per foot. Slopes between those two aren't as good because liquid "runs away" without solids. (Obviously this is even more important with toilet drains...).
That said, although the drain slope from the sink trap to the area by the fuel fill was in the correct range, after that it slopes more than 1/4" per foot, but less than vertical. I don't put a lot of solids down the sink, so it hasn't been a problem. Anyway, just mentioning that as background (and obviously in an RV it can be affected by how level your rig is).
So for me, I had to do some mockups after I had the original sink out. I also wanted to position the trap a bit differently so that it would be less in the way of a drawer. I planned to make my countertop 34" from the plywood subfloor (which is around 1-1/2" higher than stock in my rig). So I did gain a bit there. OTOH, if I went with a sink much deeper than 6-1/2" and/or the drain wasn't at the rear, it could become an issue. So I had to just mock things up and juggle them around. One tip is that ADA versions of sinks often have the drain at the rear vs. the center, which means you don't have to keep going as far (so you don't run out of slope).
Another option is to re-do the drain pipes and lower them slightly. Mine came up to clear the fuel fill, but they cleared it with more room to spare than necessary. OTOH, that means cutting drain piping that's kind of half behind the shower, so a bit of a pain.
Another possible option is a Hepvo trap. That might or might not save you anything. I've been meaning to ask them how/if they work for people like me who oftentimes just put a trickle of water down the drain (vs. a "heavier" rush of water). I'd LOVE to put a Hepvo on the shower drain, so it wouldn't siphon when traveling, but getting under that seems like a really painful chore. And the sink doesn't have that issue.
Anyway, back to the kitchen sink. I came up with a few that would work for me without major change to the drain plumbing. I was already doing some change because I wanted a single bowl sink vs. two dollhouse bowls. I don't like super deep sinks so that wasn't a problem except it's hard to find any that aren't a mile deep these days! Also there is the issue of depth (front to back). Many common sinks are around 22-1/2" in that dimension and that's too much for my setup. OTOH, boat sinks are often *too* small in that dimension (like say 15" front to back).
A few I put on my short list:
1) Blanco Rondo in stainless. Around 18-1/2" diameter (round), 6-1/2" deep, and the drain is at the rear.
2) Elkay LR2219. ADA versions have some depth and drain location options. Is a square around 22" wide and 19" deep. Has ledge for faucet so that doesn't need to be added to the total. Just also makes a similar sink.
3) Blanco Precis. Really nice, faucet can be off to side, built in drainboard. But quite heavy, so probably off the list.
4) IKEA has a couple that could work, although some of them seemed a bit cheapish (thin metal, etc.). I strongly considered the Hallviken in black though, as it was a good size. They now have the Narrsjon, that might work (but they never give the depth
and it looks deep). It has no faucet ledge so you'd have to figure that in as well.
For me, when it came down to it, I decided I probably didn't want a black or composite sink. Stainless is durable, shiny, and relatively lightweight, which puts it back to the top of my list.
BTW, if you do want to re-do any of the drain plumbing and haven't done so before, ABS (the black pipe they used) is pretty easy to work with - just make straight cuts, de-bur, and plan things out before gluing. Then support it afterward. Some municipalities don't allow ABS in houses, so in those places it can be a bit harder to find, but usually someone has it. You can use either regular or "tubular" plumbing for the first section coming off the sink bottom.
One last tip. When my remodeling project was put on hold, I put the original counter and sink back, but attached to my newer plumbing run. Thus I ended up with a relatively straight (albeit) short run of tubular plumbing before the trap. This vs. a straight vertical shot into the trap. I know this is fairly common in houses (for example, with a double sink there is a flattish run to the trap from one of the sinks), and the original Chinook had this somewhat too, but I'm going to be VERY sure to have my new sink's tailpiece go vertically into the trap. Reason is I often use minimal water to conserve, and that resulted in that "flattish" section of tubular plumbing before the trap getting a bit gunky. Yuck. I took it apart and cleaned it and now am careful not to put certain things down the sink for now. In my end design that piece will be gone and the single sink drain will go straight down into the trap (which is where the "odor sealing" starts).
BG
PS: If you have a Concourse, the front-to-back dimension of the sink is not so critical, if are willing to give up the "ell" (having the sink section do that makes for lots more sink front-to-back room). In my case, I like the ell, so I plan to move the whole ell out about 1-1-/2" (so it butts up to the molding on the outside corner of the shower), but I wanted to maintain the ell's "ellness."
Given that arrangement, I found myself always just using the front one (especially back when I was doing the "microwave cabinet limbo").
) I've never had a flame blow out (but it could), however one time I went into my buddy's rig (he was outside) and the whole thing REEKED of gas. As it turned out, three of us were in the rig chatting previously, and he was standing up and sort of leaning on the range countertop area, and he'd inadvertently turned one of the stove knobs. On the RV style stove, this allows the gas to flow. Combine that with a less-than-sharp sense of smell (him) and .... gas-a-palooza. It happened again a few months later and after that he bought a Force 10 3-burner range (he has a larger rig). That of course re-kindled my appreciation for those. Dern! They are expensive and I really don't need an oven. But, but, but...
Well, I'll probably go with just a cooktop, but we'll see.