It should work.
Some suggestions:
1) generation of the excitation signal: you could use the pwm generator in the mcu to do that.
2) excitation frequency: I would think hard about using 100khz signal, especially if you are primarily measuring large (1100uf+ capacitors) - the approach here is essentially measuring the impedance of the dut. Large capacitors tend to have high ESL and at 100khz, it could overwhelm your ESR. I think 10khz is a good compromise.
3) simplicity: in the first schematic, you have a discrete amplifier, taking a differential signal from the bridge. That differential signal is further amplified by the opamp (against, configured differentially). I would do away with the discrete amplifier.
4) simplicity again: there are some mcus (atmega32 for example) that have differential adc with high gains. They are superbly suited for this application.
5) mcu choices: In a different thread, I started something like yours (however, totally different approach), using a 16f684. I eventually ended up with an avr, for its speed, and adc. You may look at that thread and see if it could be of help to you.
6) nulling offset: I think you will find extremely useful if the meter can null offset, generated by either the oscillator or the amplifiers along the way. If the excitation signal is generated by the pwm, you can turn it off to null the offset; if externally generated, you can short the excitation signal (split R1 and insert a pin from the mcu in between the two resistors now consisting of R1) to measure the offset when the input signal is 0. Offset, in situations with high gain + discrete parts, will drift and a mcu-based nulling at the beginning of each measurement would be very handy.
Hope it helps.