Congratulations on being able to retire before 55!
A "B" van will definitely take care of your parking concerns, I have a Promaster Travato and love how nimble it is driving and parking.
Renting makes sense for a couple times a year, but one of the advantages of a "B" is the tendency to use it more. I take mine to work at least once a week, and we usually use it every weekend for shopping trips and such. In my situation buying a larger rig didn't make sense, because I know how much time it would be sitting in the driveway un-used. A compact "B" Van is a much more versatile rig: it is not for "vacations only", and should see a LOT more functional use than bigger RV's.
The prices (per square foot) ARE high. But it much more difficult for an upfitter to build a B in the confines of its body, than it is to build on the back of a flat bed truck, and then put up the walls. As you have seen, The "B's" also retain their value far longer than the "C's" and that is for good reason. One of the biggest in my opinion, is that they do not have the above mentioned built up walls and roof, which historically have led to leaks and problems in "C's". You can find a lot of "hardly used" "C's" around for the reasons mentioned above; they are usually unwieldy to drive, underpowered, and inconvenient for use other than a long camping trip at campgrounds.
I can't really comment on other brands. Pleasure Way has an excellent reputation, there are thousands of good old roadtreks on the road (though I'd caution against the newer "high tec" variants), and I am nothing less than ecstatic about my Winnebago Travato. I considered having a van built before I bought mine, and I too was convinced early on that the Promaster was the best chassis for RV use. AFter 12,000 miles I've had one complaint: A mud flap fell off... The biggest difference between brands might just be the floorplan and amenities you have on your "must have" list. You will probably find that most "B" RV owners are happy with what they bought, because they bought what fit their own personal needs best.
I also agree regarding the MB. 24' is too long to park easily. The long skinny, tall format does not lend itself well to RV's in my opinion. I prefer the handling and "get up and go" of the Promaster, and didn't want a diesel with all its expensive pollution control problems. People like to talk about how a diesel can last twice as long as a gas engine; and that may be true, but what will it cost in inconvenience and maintenance to get you there? At the premium you pay for a diesel, you could probably BUY a second gas engine if you really wanted to keep the vehicle that long. Just my opinion of course, diesel lovers will argue with me, and what can I say? ..they are wrong...
I have no help for your dog issue.
"Boondocking" is not a big deal. We spend about 1/2 our time out camping in places other than campgrounds. You just have to do it, it comes easily in a "small" van. It takes a special kind of person to be willing to trade the "comforts" of a larger rig for the convenience of a "B". It's my guess that is why salesman towards to gravitate to selling them. They feel better on the showroom floor, it's an easier sell. I still get a bit envious of space and storage every time I step into a big lush RV, but the envy quickly fades when you think about driving, parking, maintaining, and actually USING the behemoths
. They are nice once set up at the campsite (if you can fit in there), but after that, nothing but trouble in my "not so humble" opinion. We are very active too though, and spend the majority of our time outside the RV. It has a comfortable bed, a functional compact bath and galley, and gets us where we want to go in absolute comfort; that's all we wanted.
Your trailering concerns are also valid. To me, its limited towing, and lack of a tilt wheel are the only things I could think to improve on a Promaster. But again, it's personal, if you can get around the towing, I definitely think you are headed in the right direction.
And one more note: regarding mkguitars bit on bathrooms. One of my wifes "must haves" was a larger shower (hard to come by in a B). We have used our shower in the Van, ONCE to date... and that was me, in the driveway, just checking to make sure it worked! Showering in a van (any van) is going to be cramped and difficult at best. Water supply when not hooked up is very limited, and there is not much room to dry off, spread out your clothes, change, etc. We always use campground showers, so think hard on that if it is one of your deciding factors. Though a useable shower is nice, and it wouldn't have changed my mind on my rig, shower size won't be high on the list NEXT time I buy a Van.
Good luck, happy shopping, check out as many as you can; there is nothing that compares to driving, sitting in, and going through the motions of living in your prospective rig. We were surprised to find in some of the older style vans (and even some layouts of the newer MB's), we couldn't even pass each other in the aisle. That was a deal breaker for us.