Looks like there is just a simple bus bar to power the bulbs.
I think it would be very easy for me to design a PCB to accomodate the LED's and possibly the electronics.
Its even better than that....
The bus bar section actually unclips and leaves you with the front reflector housing. The holes for the bulbs are, wait for it, 5mm so take a LED perfect
1) Insert 10 x High Powered (0.5w) RED LEDs (currently winging their way from Hong Kong) & hot glue them into place to stop them moving around.
2) Wire them back to a small perf board holding an ATMega328 MCU, Timing Crystal, 5v Voltage Reg Circuit & associated resistors etc. (est size 50mm x 10mm x 5mm)
3) Locate the perf board in the brake light housing given the space gained by removing the old bulb unit.
4) Connect to +12v & Negative of brake feed
Total cost < £15
All I am waiting for now is the new LED's to arrive + some ancillary components.
Just wire all 10 LEDs to come on as normal and stop being a small child...
... however, I always did want to drive Kit.