It's a possibility - obviously unlikely though. I'm sure people would have noticed if there was a magic magnet mounted somewhere inside their Rim's. Just drop your bike in a huge box of paperclips and see where they're attached to afterwards ;-)
Wasn't sure if any of the rails used the rim magnet as standard or not or if anyone had tried it as an easy fix. The sensor option had to be changed by a dealer previously unless they have enabled both by default with the latest update.
Things to keep in mind with the rim magnet.
If you want to de-restrict - this will be CONSIDERABLY more difficult.
The field strength is monitored and can error if it thinks the strength is incorrect (too near/too far away) so it possibly needs to be calibrated as well as "enabled". (Hall effect)
Theoretically you could run a slightly smaller magnet if you mounted it inside the rim as it would be nearer the sensor, but this would lead to it's own issues.
Remember, if you buy one of these magnets (EB11200015) and run a presta valve (Which you probably do), you also need the sleeve (EB1120002S):
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