Nice to see, that other people like my vision!
What would be needed?
I like the concept of a similar GUI for different applications,
so it is easier to learn the others once one can handle one.
It was easy for me to learn Illustrator as I was used to the
GUI from Photoshop.
And InDesign was just like biting a pie, related to learning
curve triggered by the similar GUI and UI concept.
I guess what would be needed first hand, would be an agreement
by a certain group of tools, lets say scribus, inkscape, gimp and blender.
Blender would be a quite interesting project to ask,
as the have integrated some other smaller tools into their software in the past.
The also have a strong going and looking Foundation in their background.
By bundling knowledge and skills, all tools would grow stronger.
So much for the social level.
On the technical level, the software would need to get a little bit more abstract.
A unified GUI Layer, a unified RENDER Layer and so forth.
For this a strong, well thought trough technical concept would be needed and
approved by some designers. Maybe one could get some strong players into the
boat, like Valve software?
A centralized userbase, like a centralized help section, forums, howto page (like adobe is doing (bad)),
central plugin api and plugin system (maybe easy by using a centralized render layer) so it is easy
to get all the plugins out there inside the apps (just for instance)
Such a project would need around ten years to get going.
around five years to get the concept done and the first software versions to ship
and an other five years to get everything right and the community running.
And by then it is way time to get new ideas in the boat, get creative and
pass by the big ships and bring on some crazy good stuff

live free, feel happy and enjoy life!
Walter