Surely not researching anymore about sc controller... Superhonda says: 

Super Soco may be modified according to the y-cable method - you retain original throttel and control (because of all other functions thats are buid in there; display, speed, on/off, alarm, lights) but connect in parallel an extra controller and and trottle with is connected directly to the motor.

Do you mean connecting the scoco battery to both controllers (y method) and the existing supersoco trottle an the Bosch 3Kw motor to the new controller?

Would it be worth if Bosch motor is only 3Kw peak (60Vx50A)?  Not necessary changing hub motor also?

Thanks a lot

Yes - as there is no (known) way to directly “patch” the original Soco controller, adding a second controller with better amps – often called a "dual controller setup" – and let the new one be connected to the motor while the original controller faces the rest of the system and keeps the display to show all data.

See this thread;

https://supersocoforum.com/forum/main/wow-my-dealer-tuned-my-tc/#post-352

Here is a link to another electric scooter - NIU N1s  that has a lot of components for trimming on the markets in China;

http://www.myniu.org/making-the-n1s-faster/

The controller seems to be the weakest point in Socos setup, the Bosch motor is the strongest.
If you dont want to change all components (bigger battery, more voltage/amps, new controller and a new rear wheel/hub motor), I would go for a new controller.
The original controller is limited to 40Amp, so the electrical folmula is;
60V * 40A = 2400 watts, even if you start with 67V fully charged battery;
67V * 40A = 2680 watts, (Maximum motor power is 3000watts)

A new controller with 50A 60V * 50A = 3000 watts (67V * 40A = 3350 watts )

You can use a controller that is rated for some more volts/amps than the motor is rated for as long as the motor is not getting too hot while it is in use.
I have sucessfully converted systems from 18v to 24v and 24v to 36v using bigger batterys without changing controller or motors.

Agrees that research and finding knowledge are as fun as driving ...

I dont think the both controllers need to communicate, but I think in the NIU:s case, when only the new controller is connected to the motor, the Y-cable is a refining that can give exchange values for speed signal and throttle position etc.

But the idea with two controllers is to feed the motor with more power than the original controller can do.
So when keeping the original setup with trottle and controller you will unlock and start the system as usually and then leave this throttle and controller at "idle" (as you roll of a slope) this systems than will show speed and battery percent in the display, and let the lights work as normal etc.

Meanwhile the second controller and throttle feed the motor with more power than the existing controller is capable to do, giving you more acceleration and use the existing motor to its maximum.
Nothing is destroyed and removing the extra stuff can make everyting back to stock!

But if that not is enought and you want to go bananas, a bigger battery with higher voltage/Ah:s, a new controller and a new rear wheel/hub motor you can replace everything, probably you can find a new controller with a nice LCD display that can replace the existing.

I herd today from dealer the TC MAX will be available next spring with an on road cost in £ of 4K. Do you thinks it worth just waiting till then and trading up rather than trying to modifying it your self....?