Solution? Find a couple of images on the internet and become inspired. I give you...the Rhino Russ (actually there are two of them).
The Predator version using magnetized Sponsons and the turret deck plate (simply placed on the model) w/ aftermarket "Deimos" style turret and magnetized autocannon.
Body consists of a Rhino chassis trimmed down...crammed between Leman Russ tracks and then the back end is made from card/plastic/bits to fill it out.
Aftermarket resin exhaust stacks on the back sides.
The rear Rhino gate is kept...even on the Predator (sadly!)
Sponson heavy bolters will be magnetized or glued in (I may just make spare sponsons instead)
The Rhino version features the basic Rhino deck plate and simple hatches - I only have one pair of hatches at the moment - more on the way. Note that without additional vehicle wargear, the Predator will not have the twin-linke bolters on its hatches.
I find this "version" matches marines a good bit better - and is very Horus Heresy era looking - more robust and brutal.
The weathering is sloppy at best but I've never painted tanks before...so mostly hand-painted scratches with some additional foam slaps.
Planning to have a third one sometime soon - I will do a full "how to" build post now that I know it works and is possible.