My idea of implanted decks and commlinks include them having the UDC ports and other such ports still available from the outside, so you can still use cables and such.
The hardwired module likely wouldn't increase the bulk by much, or I wouldn't make it. It shouldn't change essence cost though, if anything it'd be an odd lump on your head.
The dongle though is, by name, a UDC-port dongle, like a modern-day flash drive. So using it would be possible, if you didn't mind having a plastic chip sticking out of your head. It may not be very big (like some modern wireless mice's dongles) but it could be uncomfortable if you had a helmet on...
Long story short, some flavorful appearance issues and some odd looks, but no mechanical change.
