That is quite similar to what I am planning, but I will still do an "H" drive version instead because it is much simpler.
I recently updated my carriage assembly to lower its mass (pancake motor and custom printed parts) and made it more rigid.
In the end I gave up on Bowden feed completely.
It worked but was just too troublesome in regards to stringing and blobbing.
So far I am pleased with the present setup and can print at 80-100mm/sec all day long.
I also recently converted it to a three point bed leveling arrangement which works great.
The "H" drive conversion is next on my hit list.
As far as the larger Z rods go, it is nothing but good, however the double bearing setup I have on the 8mm Z rods works fine too.
Because the bed motion only moves up and down and the framework is heavily cross-braced, I really am not seeing any lateral movements of the bed plate.
And no tilt either any more.
Another forum member recently tried this as well and reported being pleased with it.