i think you know what i'm going to suggest.....

the regulator connector has been the tenere's achillies heel from the start, the earth fails as imho the connector is too small as it has to create a circuit for charging as well as dumping excess voltage to the frame to stop the battery from overcharging.

the fazer600 or fz600 is definately the way to go. straight fit, excess wire to allow joining and the ability to point the wires downward it gets no better!.
though plenty of other makes should do, honda etc. though not kawazaki klr they use 6 wires, the extra one is connected to the ignition oddly enough.

it is really a simple straight forward bit of kit just 5 wires to join properly following the colours, mount it and your good to go!

don't ever mention bmw reliability [or lack off [not a fan!]]


hope you get it sorted soon! bernard