Until now, the bbs01b is too expensive for what it is, there is also the issue that many customers need a gear sensor and also can't replace the controller in them.
However irrational this may be: I believe one reason why the gear sensor works so well on my particular bike, is the straight cable run through it, and situated on a chainstay, rather than dangling and bobbing about kinking the cable under the handlebar. You could perhaps make user installation easier by glueing the sensor's end ferrules onto it's housing and outer cable, and supplying both complete with the sensor situated in the middle of say 8m of outer cable? Users can simply cut off the excess depending on where the sensor can be situated on their bike. Wasteful, probably unwise, costly, but may make fitting easier for your customers? Longer ferrules could work out better.
My gear sensor continues to work wonderfully three years on. As you can see in this photo of my awesome bike (gaze upon it's beauty and weep, for it will never be yours etc. etc.) both ends are protected from dirt and water by self-amalgamating rubber tape, which over the years has been moved a bit by being pulled forwards by the gear cable, but the sensor remains protected.
Andy wants to call it the Anaconda
WOOSH!BigTorqueBiggerTrousers™ ®©
Advertise a 15A controller, but deliver 20A to avoid being stung by the Trade Description Act enforcement guys - if you get a lot of controller failures at 20A, ship 15.000001A controllers instead. Free huge trouser shaped rain cover with every bike. It'll fly off the shelves.
Consultancy and royalty fees to my Cayman account will be fine.