I can't speak to your issue about modern ventless dryers, but, back in the mid 60s I had a Maytag Porta-dryer which didn't need to be vented. It could be - but it was a 3"vent hose I believe, because eventually we vented it when we moved. I used it in an apartment when I washed diapers in my Sears porta-washer which if I remember was sort of full sized, but small capacity. it washed 20 diapers and the dryer dried that. We lived in a residence hall and I hooked the washer up to the sink and the dryer vented into the room. I put an old stocking (those were the days) over the vent with a rubber band to catch the lint. Drying outside wasn't an option, and we only had two rooms so hard to hang things all over. It was before Pampers. I don't remember much humidity but we lived in the northeast and had a room air conditioner back then. Anyway, this is a nice walk down memory lane and I guess I'm not surprised there is a solution to almost every problem.
I hope you will let us know what you end up with and how it works.