Electric off road bikes could potentially open up a lot of riding areas because of the noise reduction.
your exactly right, already exists with small bodies of water being electric outboards only. The environmental impact (of where your riding) is almost zero so you wont be any worst than a Mtn bike or a horse. As long as the 'idots' dont wreck it before it gets going this could keep continued access in a lot of places.
They have no idea that is has to be generated some how. Perhaps the acceptance & development of electrical powered vehicles will be in conjunction with the development of the means to generate electricity cleanly, efficiently, & hopefully economically too !!