[Argus25]

Ok, that makes it clear now what you are doing.

It is important then not to draw any significant current from the divider chain.

One way that would work, which solves all the problems but one, would be to use miniature reed relays, the coils being easily controlled by the logic circuit and would give all the isolation required, but I suspect there will not be room. Using the mosfet and driver transistor, you would also need a fairly high value of gate source tie off resistor, so the load on the line you were switching was very low.