You don't need a beacon as the Rollcentre lap timer picks up a signal from the circuit beacon anyway.
Right, back to your questions...
1 - You can change the internals of the forks, but the actual fork must remain a 620 fitment. In other words, you can't fit forks from a 999R!!
2 - Cheaper to twist the throttle faster. Try masturbating to increase wrist speed.
3 - Rollcentre T100 (secondhand on ebay?) or T200
4 -
Nitron Shocks are brilliant, but same money as Ohlins? Maybe.