I will be waiting to see your options as well. I would like my spare out from under the vehicle as well. It's nice to have it out of the way & all but that's also the problem...It gets forgot under there and suffers all the road debris , dirt/dust/wet... but never gets a wash or any attention. I guess if your smart (I am not) you do a 5 tire rotation and at least that gets it in (the loop) for some tire care. It's sorta a catch 22 on this one. Anywhere else you put it cost quite a bit of $$ for the mounting and it usually is a lot more in the way than when it's tucked away underside. Also when looking into this myself I heard (some) complaining about the issue of lifting & dropping down the thing from the usual back door or trailer hitch mount locations. Not a young strong back mans problem but many are older with back problems...
Just including this little bit of extra info for you to consider before you spend $$ for nothing or realize it might not be as good an idea as you thought to change it's location. (unless there's some very specific reason you need to move it).
I could add my best advice on tire's/rims/lug nuts & having to change tires here also. One of my best purchases so far has been new lug nuts that COVER the threads when installed! Now every time I take a lug off it is unscrewing on clean fresh threads. NOT dirty banged up and binding or stripping threads that have been exposed to thousands of miles of exposure to above said same road debris. Plus they are chrome & stand off nice against the black painted steel OEM rims. Just sayin'
Maybe it would be better to figure a way to mount the water tank somewhere (up) there where you might be thinking of putting the tire???? I have this idea that I am going to someday put a ladder rack system on and attach 2 maybe even Four, 4" diameter PVC pipes to it and withe the appropriate fittings fill them with water. Paint em' black to heat the water. Forgot the calculation I did that came up with the gallons a 4"x 10 foot long PVC held. It was more than I thought. Then I had to start thinking of all that top weight. But if you drive cautiously & don't go screaming into highway off ramps it's (probably) not a problem. Plumbers have them full of copper & steel pipe & I don't hear a lot about their set ups being a big risk (as long as ya drive properly for the load). JMHO
While having lots of water being heated on the roof for free sounds good...
I already have a high top with solar panels. And that extra weight would/can effect the handling of the Van.
I'd like to have that weight as low as possible.
Moving the tire might me a pia, it seems safer and easier.
I have the Ruenel tire carrier mounted on the stock step bumper (ala Sportsmobile style). Apparently, Ruenel themselves do not support this application, which is why I had to order it from SMB. True, there are potential issues with rattling, but only over time and allowing it to get loose, in which case you can tighten things up. (I have a transfer flow tank in the old location.) I also mounted my hi-lift jack on the inside of the mount for a unique look.