How about that one:
I don't know about that. If Switch was supposed to play 3DS cards, then it would already play them; besides, by the end of 2018 it wouldn't be a desired feature anymore. Your estimate for cost savings by ditching the dock and Joy-Con grip are too high, because accessories have a high mark-up.
Above all though, I don't consider Switch pricing to be so bad that we would need a $150 (or $180) model by the end of 2018. Price cuts and revisions will eventually come, but I don't think they'll be close to your ideas.