Mini and micro usb seem to be rated for something of the order of 5k and 10k respectively - not surprising since the latter is in phones, and it looks like the most stressed part in micro has moved to the cable:
http://gct.co/usb-connectors/(not the most definitive of sources, but I can't be arsed to locate it in the usb specs..and particularly since I've written this once already and lost it
)
Oregon/Etrex/Colorado are IPX7, so you can supposedly drop 'em in a metre of water without any issue:
http://www.garmin.com/en-US/legal/waterratingTBH I'd be more concerned with permanently powering a device externally with the usb cable being jiggled around - in rain or otherwise. Is that why yours are stuffed, Ham ?
For on-bike charging, QI looks like it can provide max 5W in low power, at mebbe 50-70% efficiency. Assuming you can run an Etrex on (2500mAh?) for 24hrs - 104mA for an hour (which sounds the right kinda ballpark) that's about 1/2W @ 5V - certainly if you had an on-bike charging cradle you wouldn't notice a watt or two if you effectively hung it off a dynamo. Tho' I daresay some weight weenies would then complain about the size of the cradle/charging puck - and you'd need to make that waterproof too, including any connector if there was an extension power cable to it..a different can of worms.
It'd be interesting to know how many users would actually *need* that support - I suspect most are probably more than happy swapping AAs or plugging in to charge, so it'd be extra engineering/cost for what might be a relatively small proportion of customers.
(Note that 'most' above does not necessarily include the Audax crowd..)