I don't know about the middle ground, I'm not really sure I can relate to that at all. I'm mostly top oriented, but I have some very specific fantasies I'd like to try as a sub. I'm really not sure if I'd call myself a switch or perhaps switch-curious?

I can understand other people being frustrated by thinking they're not going to be everything you need, or that you won't reasonably fit their relationship. If I found a domme to try subbing for I would expect some kind of annoyance (maybe not the right word?) for thinking I might break the exchange of power. But I'm a firm believer that each relationship is different, and can fill different roles in your life; you don't necessarily need to be poly for that to work... I mean, most of us have had vanilla relationships also, and those often satisfy a different part of what we want in a relationship.