Welcome to the group. I too am a new member to the forum and just recently purchased a new 178 to enjoy in my recent retirement. I also spent quite a bit of time trying to decide which bike rack to buy. I tried to decide whether to get a rack that utilized the existing trailer hitch (displacing the spare tire), mount on the A frame (causing more tongue weight and worrying about bike clearance with the tow vehicle on tight tunrs...along with what looked like much more expense to do on the A frame), mounting the bikes on a roof rack of the tow vehicle (a pain in the ass to get up on the roof of my Highlander AND causing more wind resistance to the already burdened issue with a trailer). I realized that all my options had upsides and downsides so in the end I decided to do the least expensive and easiest solution for my scenario and bought Swagman XC2 bike rack that utilizes the existing trailer hitch on the R-pod. I will simply keep the trailer spare tire (for now) in the tow vehicle on my trips. The Swagman XC2 is an excellent rack for the money (hold 2 bikes) and I recently saw it as cheap as $113 at Amazon and online at Walmart. This rack works on both 1 1/4 inch and 2 inch receivers (comes with a adapter sleeve), so I can use this rack on my trailer and tow vehicle separately when needing to do so.
The only mod I have done in relation to storage probably isn't really what you would call a mod. When I bought my 178 we were considering a 179 also. There is much more storage in a 179. My wife and I both preferred the floor plan for the 178 over the 179 so picked that. One of our first moves was to buy a $8 or $9 "over the door" shoe rack....or shoe organizer that rolls up and each shoe holder/pocket is made of net so you can easily see what is inside the pocket that was originally designed for shoes. We hung this on the outside the door for the wet bath and it works magnificently. In one swoop we in essence created a pantry that holds a lot of items that pretty much solved our entire storage issue in one cheap easy step. The one we purchased as luck would have it is the perfect length stopping just short of the floor and giving us a surprising amount of added storage that is also incredibly handy. I am reluctant to try any more complicated mods with my new trailer :)
Welcome to the group and have fun with your 171.
John