Well I think you've covered the most obvious and likely most useful scenario for Tasker integration. I use tasker a ton and I could easily set things up such that when I reach a certain distance from the house the thermostat does something or the lights do something.
One nice thing about Tasker (and Zoom, an app by the same developer) is the ability to make custom "scenes", not in the Insteon sense, more like apps/menus, in addition to custom widgets. I can imagine all sorts of awesome looking control panels that could be made on tablets and phones with a MobiLinc plugin. I'll be honest with you, the current widget support of the Mobilinc app is pretty poor and I wish there was more customization of the layout and sorting within the app as well. With an extensive Tasker plugin that would at least provide an infinitely customizable way to interact without Mobilinc having to develop their own from the ground up.
The success of this plugin will definitely be dependent on how much control/access it allows from Tasker. If it's simply turning devices on/off then I wouldn't expect much enthusiasm for it. If it allows all the same controls as the Mobilinc in-app details screen then we're talking some real potential.
I can't recall if plugins can be used to pass strings back to Tasker for use in variables, pretty sure it can, but that would be huge.
PS: and I'm willing to beta test.