Think you are missing the point with so called work arounds.
In your RA example it usually is not the system that is a no dispatch as it is based on a redundancy architecture.
However the place in the rack is paramount due to the units wiring ie. power supply or as in the LGCIU1 example hard wired to the three greens. (plenty of threads on that one)!!
With the tachometer example again the BSCU uses the information for WHEEL SPEED and if the brake is released hence no dispatch. To be fair this is a recent addition that Airbus have obviously felt that 4 must be serviceable, we use to be able to dispatch with one inop.
A better work around would be to make the anti skid system u/s and tell the skipper he/she is on alternate braking at 1000 psi.
I doubt they will take it!