Do you have the spec sheet for the mic? This source says supply +5v on Pin 2 of the circular connector.
I wouldn't go cutting any traces.
1. Supply voltage thru pin2 of the circular connector and use the modular connector for connection to radio
2. Add additional wiring to internal circuit board for battery/power supply
3. Wire up circular connector for connection to radio, but with breakout wiring to power source
4. Modify the radio to provide power thru existing pins.
QRZed: "Professional Grade Paranoia From Amateurs"