How critical a resistor value for MSP430 spy-bi-wire on reset?
I would expect that several factors will put constrains on the size of the pull up resistor:  


It must be big enough such JTAG driving circuit (programmer/debugger) will be able to override it,
It must be small enough that leakage current/noise will not change logic value of the line,
The RC constant that remove /RST after supply ramp up will have to be chosen to ensure proper reset.


Check documentation of uC and JTAG programmer for leakage and drive strength. Based on that size your pull up resistor. I would try to keep RC constant the same which would mean re-sizing capacitor. Note however that schematic you posted put maximum restriction on the capacitor to 2.2nF.

Standard disclaimer: You should follow manufacturer recommendation. There is good reason for that as good gals and guys that made the chip may have put really strange things into it (that are just waiting to bite you). What is worst such things may not be documented as describing them would reveal trade secret. If needed contact your support channel (usually not possible for small customers or DIYers - in this case experiment!). Note that I am not affiliated with TI and I do not have "inside" knowledge of the device.