Doubleclicking is indeed the way to do this currently, but I vote for a better way to equip gear. F1 and F2 and etc. keybinds of a secondary bar should be fine, but ultimately, it should be a keybind that users can change to what they wish.
I could also recommend only two keys, Q or E and [ or ], to go left and right on the available items in the hotbar. So I place a rebar gun, a taser and a food item on teh bar, and using [ I move to the next item on the left of the currently equiped.