Control board upgrade?

[tenaja]

I have no idea how variable width extrusion could ever be possible with a fixed nozzle size and

Not to be insulting, but I can not fathom somebody with that narrow of knowledge or experience base being qualified to evaluate or even doubt whether any control change is an upgrade or not. These are all features that slic3r has (it is installed on the Hyrel from the factory, and is tightly integrated into the software). Read the paragraph preceding the first image:
http://manual.slic3r.org/advanced/flow-math
In use:
https://farm1.staticflickr.com/527/2...1ac3fc6c_z.jpg
Also, it is well known that in certain conditions you want a thicker first layer. See the very first sentence of this slic3r page:
http://manual.slic3r.org/expert-mode/extrusion-width

I don't know what variable height extrusion can even mean.

Variable height extrusion? Slic3r has it:
http://manual.slic3r.org/expert-mode...e-layer-height
For someone who has used other systems, it does not take long with a Hyrel to realize the controller needs upgrading in a bad way.

For sure if you want it as capable as it can be then Linux CNC is the way to go. I didn't say that the change was premature, I declared calling it "an upgrade" to be premature.

Based on that statement, I guess you have little experience with other systems.