Loaches can do withouth plants, and plecs really. They prefer caves and nooks and crannys. Plecs like bogwood, in fact I think they need it for digestion or something.
Problem is nothing will remove your Nitrates for you, so may mean more water changes, also plants help 02/c02 in the tank.
Most vegetarian fish like plants, gouramis, silver dollars, mollys, plattys all like plants, livebearers like plant cover for giving birth.
I know why you would want it, but I personally wouldnt have a tank without some plants, as most fish do like them, even if they dont 'need' them. They give good cover too.
Could you use some planted bog wood ?