Hi Waz,
No need for programming. Help is at its way 
The message already tells what the problem is. You have installed the addon twice. And this is not tolerated. Archimesh already comes natively with Bforartists. There is unfortunately no way to uninstall addons from within Bforartists / Blender. You need to do a bit hand work now.
I hope you are at Windows. I don’t know the paths at Unix / Linux.Under Windows you need to navigate to the Appdata folder, and uninstall the addon from there. Hint: This folder may be hidden.
The path is: C:UsersYOURUSERNAMEAppDataRoamingBforartistsBforartists2.79scriptsaddons
Simply delete the archimesh addon from there. And then activate the one that comes with Bforartists already.
As a sidenote, i have installed the Archipack from Github. This addon also includes Archimesh. But runs without conflicts.
And a second side note, we don’t have the Add menu anymore at its original position in the header. It is now in the Create tab, and just meant for addons. Like this archimesh addon. See screenshot …
Two questions/suggestion about bforA; can the toolbar icons be enlarged/scaled up? Or dockable into pallettes? If not, be nice to have these features.
Unfortunately not, and i haven’t found a way yet to implement it. The icons size is hardcoded appwide. And customizable toolbars where you can add your own tools is a very special chapter. But Blender devs are working at something like this for 2.8. And so we might see it in Bforartists then too.
What you can do is to scale the whole UI a bit bigger. User Preferences, Interface tab, Display Scale. A value of 1.1 can do a miracle already.
Hope that helps 
Kind regards
Reiner