I've been planning on this setup for months and today I finally have the time to set it up to show everyone the idea.
As you can see the most important element is the SG4 which is mounted under the objective of the scope. This can highly lower the torque and in some way lessen the demand of the amount of counterweight. The setup in the photo is perfectly balanced, so you can see the counterweight is only half-way down the shaft.
A T-mount camera lens of 135mm F3.5 is attached to SG4 (i bid it on Ebay).
There are still some hardware issues like wiring and initial setup of SG4 to test and deal with, but all in all I'm quite pleased with the fact that the idea finally worked out. I no longer need to deal with the flexture and cumbersome side-by-side guidescope setup, and when compared to my original setup this thing is at least 5kgs lighter (and I haven't taken into consideration that the amount of counterweight can be further reduced.)