Rearsets and brake switch

I haven't looked at the connections myself but I expect that the extra two wires are to disable cruise control when the brake is applied.

I see two options;
If there is no way to mount the OEM brake switch perhaps you can use a multimeter to test the connector on the brake switch to see which pairs go together. If you're not going to reuse the brake switch you can then cut the connector off and solder the two wires from your pressure switch to each pair on the brake switch connector.

There is some risk to this without fully understanding how the internals of the brake switch are set up and how the ECU reads that the rear brake has been applied. When the brake switch is closed you'll have current going through it to power the light because as far as I know there is no relay for the rear brake light. If you solder the 2 pairs of wires into one you would be sending this same current to the ECU. The fact that there are 4 pins to the brake switch instead of two indicates a possibility that the brake light and cruise control circuits are separate inside the switch.

The other, and in my mind safer option is to run jumper wires between pairs of wires on the bike side of the brake switch connector and see which activate the brake light. Wire up your pressure switch to those two wires and understand that the rear brake will not disable cruise control, or do it vice versa.

In addition to the brake switch, I would also address the lack of an adequate return spring by adding a Woodcraft return spring kit to the master cylinder. As far as the switch goes, my plan with the LighTech rearsets was to buy a used Yamaha switch off eBay just for the brake side plug. This way you don't have to splice into the wiring or sacrifice the OEM switch. I was going to use a single stage hydraulic switch for the brake light circuit only and lose the ability to cancel CC with the rear brake. I ended up having to go with Gilles rearsets due to pipe mount issues with my Graves pipe but would have preferred LighTech.

I'm looking to order the lightech rear sets as well, but Im going to wait until you get yours setup Please let us know of your progress or any other problems. and pics please! 

I corresponded with TAW and the guy basically says :

We have no idea as far as 4 wire for the FZ / MT-10.

The LighTech part is RFTR93, which is the 2 wire, and what LighTech have listed on their installation sheet for that bike.

www.tawperformance.com/lightech-hydraulic-stop-switch-m10-x-1-25

LighTech has stated that most EURO spec bikes do not come equipped with cruise control, which may be the case on this Yamaha and why they only offer a 2 wire switch, as all their data is from EURO spec bikes.

All other brands of hydraulic stop switches, that we are aware of ( K&S, vortex, etc ) , are also 2 wire units