of course also if you're covering the top with say grit or scatter anyway, or indeed filler, then make your bit of terrain, with whatever covers it, then glue the model to that, e.g. a layer of sand glued on with pva, then soaked with dilute pva becomes pretty tough, you can superglue a models foot to that.
Really depends exactly what you are trying to do, the one to talk to is big Paul, who works wonders on terrain, if anything is possible he'll know how