Possible, yes. Worth it, probably not.
The area between the Cairngorms and Loch Ness is filled by the Monadhliath mountains - the gaelic translates as the grey hills, and that's not a bad description - they're lowish, rounded moorland cut by several valleys. Up to five or ten years ago, my advice would have been that a walk through them was definitely worth it if you enjoy that type of scenery, in fairly wild and empty land, partly following hill tracks and partly walking "off-trail".
However, the past decade has seen multiple wind farms developed in the area, most of which are not yet on standard maps. The best resource to see them is probably the
Highland Council's windfarm map available here, which, if you zoom in, has very up-to-date OS mapping showing the new tracks to and around these farms as well as the location of the individual turbines. You'll see that many obvious routes across the Monadhliath now involve walking through miles of windfarm, which are probably not most people's cup of tea.
It is still possible to find some interesting routes there, particularly on the edges, but unless you've a strong personal reason for walking there I'd have said, sadly, that there are now many other bits of Scotland which I'd visit first, assuming I had a choice.
[Edit - having said that, you've got me looking at the map! If I
was going to do such a walk, I'd probably take the "Burma road" route out of Aviemore to the Dulnain valley, take a mixture of hill track and "off-trail" walking to the Findhorn valley, follow the track up Glen Mazeran, then off trail over Carn na Saobhaidh, drop down somewhere near Loch Ruthven and follow a mixture of tracks and minor roads down to Loch Ness. I've walked parts of that before and I think it would make quite an enjoyable route which would avoid most of the windfarms. Though be aware the off-trail sections have the potential to be quite hard going and boggy, and clearly need reasonable navigation skills.]
