Lightsabers are weightless on the blades and the hilts are basically weightless also. The lightsaber is pulled into grip by the force if needed quickly. It's only grabbed when needing to move slow. Lightsabers are only held by town hands if its a specific jedi. There are differant forms and some of them only have one hand and some of them have two so you wouldn't hold them always like they do in the movies.
Well you're right that the blade is weightless, but I highly doubt that a foot long tube of metal housing a power pack would be weightless as well. If I were wielding a flashlight, I still would prefer having my dominant hand on top.
Sure, pulling the lightsaber with the force would improve the speed of drawing the lightsaber, but it doesnt change the fact that you would have to hold the lightsaber with the right hand on the bottom before switching to the top.
And as far as I know, only Shien form has a different hand position (blade held in reverse). Putting aside the fact that Shien form is stupid and impractical, all the other forms use an orthodox hand position which would be hindered by the mainstream design of lightsabers.