To that end, i'm releasing here a method for getting Insecure ADB on any rooted Arc (with or without unlocked bootloader). But...
THIS IS ONLY FOR DEVELOPERS! YOU CAN BRICK YOUR DEVICE DOING THIS AND IT IS NOT INTENDED FOR WIDER USE!
Update: This is now available as an easy to use installer APK! DOWNLOAD (Mediafire Pro) - MD5: e71b01c0813af1d1cb1b449e834331ad
Note that this also installs busybox.
Enjoy - I hope this is helpful for helping getting these devices more 'open'.