Hey there, I have faced your situation myself.
My car has a 3500lb tow capacity but only 260lb tongue weight rating (made sure to do my homework) My carrier and one ebike typically is only 70-90lbs and even a second ebike would take that total up to 120-130lbs.
But, I was worried about the heat from the exhaust damaging the tires as the front wheel in particular hung quite 'low' and in line with the tail pipe (I have dual tail pipes so no option to just switch the direction of the bike).
When I looked into an extension/riser unit I learned it cuts both the towing capacity and tongue capacity in 1/2. My 260lb tongue limit now became 130lbs. Knowing that I did get an extension that comes out about 12" which is a bonus as it created space between the trunk (open) and the bike to get stuff in/out without 'tilting' the carrier down and it came with a 10" vertical lift that keeps my bike tires clear of the exhaust pipe.
Photo for reference:
This setup still allows me to carry most of my ebikes on the carrier I have, just one at a time. 80% of the time I'm taking a bike I only need one of my bikes from my fleet as I ride solo mostly or meet up with friends who bring their bikes with them on their vehicles.
But, when I want to take multiple bikes - like your suggestion, I did choose to buy a utility trailer this year. 5'x7' that extends out to 5'x8'3" with side walls, galvanized steel for weather proofing. I take the carrier and the extension mount off as a single unit in 1-2 minutes and put on my trailer ball even quicker.
Having the trailer now is amazing. I had trucks before and they're great for a lot of things but a utility trailer being lower to the ground, rear ramp to roll the bikes up onto the trailer built in - just works so well.
Sure, I do have to drive a little slower and the gas mileage with a trailer on does take a bit of a hit - want to mention those considerations as well.
In the end I now have the right tool for the situation - single bike, take the carrier - multiple bikes or any other cargo transport that won't fit inside the car - take the trailer.
If your budget permits your suggestion of a utility trailer sounds like the best solution for you as well.
Cheers