Thread drift...
To cut a long story short, the KFC225 autopilot can be fed only from two certified pitch/roll sources: the KI-256 hirozon, or the KVG350 remote gyro. The latter is a cool US$25k.
Aspen are talking about certifying a version of their popular thingy to emulate the KI-256, which will be a useful option.
Of course the advantage of a vacuum horizon is that it will always work even if everything else has stopped (assuming an engine / vac pump failure not coinciding with a total loss of all other systems, which is a reasonable assumption) so if one replaced the KI-256 with something else, and fitted an electric horizon, that electric horizon would need to be powered from its own alternator.
If one fits the Aspen, and loses one's electrics, one will lose all gyro instruments, which is not acceptable.
Technically 100% feasible and very easy but legally tricky. A stupid situation. On a homebuilt you would just stick in a little alternator screwed to the vac pump accessory drive and drive one of the £1500 electric horizons from that.