Hi Liz and welcome to the group.
First, your title
, Towing like you're not even towing?
doesn't play well with many of us, if you get the idea.... we want everyone to never forget that they are towing....
Moving ON, I'd bet that your horse trailer(s) had lot's of tongue weight
, that's a real tip off for steady towing and a common discussion point hereabouts.
And, Semper Fi isn't a common description, but do know that the Marine's Special Services Division has a number of Casita's for families to use on vacations, so I guess that saying the "Marine look" is appropriate.... (gottcha!)
Anyway, tell us a bit more about your needs. So far it looks like a 16' or 17' FGRV at a minimum, to house the hounds and a shower is a start.
More over, do you want to buy new or used, and, if used, what condition/age can you accept. As many FGRV's are still around after nearly 50 years, there is a wide range to choose from. My own Hunter-Compact-II just turned 43 this year and we just finished a 30 day/5000 mile trip without issues.
And last, what will you be towing with. Some FGRV's aren't as light
as they look and some newer vehicles aren't towing rated as high as one might think. Let us know the make, model and year.
And BTW: Contrary to what a certain Airstream owners opinion indicates, single axle
FGRV's tow without issue as well. As I mentioned, we just towed ours 5000 miles without as much as a wiggle. There are no driveway Queens at our house.
Good luck, and keep asking questions.