Hey dude I experienced the same problem you did!!! I called the company for warranty but they had none left!! so we did our own fix till the 08s came out!!!
Me and my dad fed the the new wire through like you did and then cut a small slit very close to the case so we could get the wire out the bottom like 1-3 cms from the base plate then found a small screw and screwed it upwards through the base plate and made a hole the we took it out.. so now we had a hole and a wire out the bottom of the boot still attached to the boa!! so we took the wire hanging out if the bottom of the boot and put it through the hole and put the screw in again and that way the screw clamped the wire in the hole between the screw and plastic.
Now your wire is attached again!!!
Note: put a piece of bicycle tube rubber under your screw so it doesn't scratch your board, mine slipped out and made a little scratch. even with the rubber.
Im not sure how long this will work and how it'll work for you im just saying how we fixed mine.. I got new boots after the season was over.
Hope you figure it out