Misc thoughts
Any possibility of widening your garage door by (say) six inches or a foot? It wouldn't be cheap, but your other options aren't either.
Re the Electra-Magic. First, be sure in your own mind that your objections are really the smell, and not discomfort with the whole idea of a pot o' poo down there. If the issue is the latter, go ahead with the toilet changeout, as nothing else will make it right.
If the problem is smell, there are some easy things you can try that help many people.
1. Keep the seat and the lid closed at all times. It is not a hermetic seal, but is tighter than the seal on a household toilet.
2. Use plenty of water for charging.
3. Did you use an adequate amount of a good deodorizer? Opinions vary, of course, but we use Thetford Campa-Chem Original Formula, half a bottle for an overnight stop, a full bottle for longer. We have not found that any of the more "dainty" products work as well.
4. Run the bathroom vent fan occasionally, and crack the bathroom window.
5. Be sure the flush is complete. Occasionally a bit of stuff refuses to go down. A longer flush may do the trick.
6. Install a powered toilet vent. It is not hard to do if you are a bit handy. One of our members did a real nice job, and described it in detail here.
https://www.trailmanorowners.com/for...d.php?t=19938&
It is a whole lot less expensive, less effort, and less time-consuming than replacing the toilet.
Good luck
Bill