INA139: INA139 and TPS22959 switch

Hello Peter, 

we have discussed in a previous conversation about INA139  to sense 10A current and INA282 to sense 10mA to 50mA, as shown in the picture below.

I want have the possibility to disconnect this part of circuit, i mean INA282, INA139 and Rshunt  because it's absolutely required in my application to measure a third current of 70uA.  for information,  my application contain 3  consecutive phase of operation :

Phase 1 : sense 10A

Phase 2 : sense 50mA

Phase 3 : sense an ultra low current of 70uA. this current will be sense with an external module (NI9203) able to sense between +-20mA  (i don't know if i could find a current sensor from Texas Instruments able to mesure this current).

My big issue, is it possible to add  2 switch as shown in the picture below to disconnect this circuit when i am  mesuring the 70uA current. Already, I know that logically, it is not advisable to put anything, beause it will distort the measure. 

if i use the TPS22959 Switch to disconnect the circuit,  it have an ultra low Ron resistance so normaly he will not influence to much the measure. 

1 - Do you think that it could be possible to add this kind of CI with the current sensor. 

2 - Does it exist at Texas Instruments a circuit able to measure a current arroud 70uA. the issue is to be able to integre it in the same board. 

Thank you.