Just did the boot loom on my TF and found exactly the same thing, wires crimped & wrapped in blue tape. I'd guess that it's just part of the loom because I found the same thing under the dash.
Soldering wouldn't do any harm but I'm inclined to leave well alone, at least until I start getting bother with them.
As far as repairing the broken wire goes, I used crimp connectors with heat shrink. Because of where the wire broke, I was struggling to get the soldering iron in. Just used a hot air gun for the heat shrink.
The boot loom is about 150mm too short so the cables are bending beyond their limit and at the point of maximum pivot. I have now done a few of the boot loom repairs; that crimped joint on the black earth is done at the factory (high quality British design engineering which saves 0.1 pence in production but cost thousands in faults and warranty repairs!)
I found some very flexible Lapp Olflex 8 X 1mm sq core cable, cut the boot loom about 200mm from where it comes out of the chassis loom fit an automotive male/female 9 way plug and socket with crimped fittings, make a 100mm loop with the new boot loom and cable tie the fixed end level the the boot hinge spring, give yourself some slack and cable tie the new loom along the hinge bracket, now the new cable will pivot at the 100mm loop without bending the wires beyond their fatigue limit.
At the boot end cut the old loom about 150mm from where it enters the boot inner skin, remove the boot gromit and slide it along the new cable, then cut the individual wires back in 15mm steps and the same with the new boot loom so you don't end up with a big lump at the join.
Twist and solder each pair (put the crappy factory joint at this point and individually tape each soldered joint, now feed the new joint into the boot skin so only the new cable is visible, re-fit the gromit and cable tie the new loom in the same points as the original.
The new loom will now only pivot at the loop giving the minimum cable movement when the boot is opened and closed, plus you have a spare wire for the boot popper and if you ever need to remove the boot lid you can just unplug the wiring.
Brian.