I've seen some house ruling addressing how familiars are meant to advance, given the changes imposed by Realms of Power: Magic. The most common I've seen is allowing the Silver Cord to subtract somewhat from the Might penalty. I had a similar idea that seems (to me, anyway) to allow the two different rules to live somewhat in harmony. I'd be interested in hearing opinions on the matter from people more familiar with the rules than me.
If a character with Magic Might is the familiar to a Hermetic Maga with a lab total above (X), the two can perform a short (one day) lab activity to remove the Might penalty to advancement for a previous season, conditional on experience only being spent on Abilities, and imposing an additional Gain Limit of the Maga's own score in each raised Ability.
(X) might be most simply a restatement of the Familiar Bonding Level (ArM5, p. 104), but since that total adds Might without multiplying, making it easy to reach even after the Familiar transforms significantly, a more appropriate total might be something like:
Lab Total: 10+(Familiar Might x 3)
Lab Total: 10 + (Familiar Might x 2) + (Total score in Magical Qualities - Total score in Magical Inferiorities) x 2
The reason why I think the above house rule might work well is because 1) it would limit the type of abilities Familiars would be encouraged to learn, so that it would improve specifically in a way that would allow the two to work well together, but it would likely not develop an extra pool of Abilities the Maga doesn't possess (which would give the familiar a benefit it didn't have in the original rules), and 2) because Familiars cannot learn Arts, while Hermetic Maga splits experience between Arts and Abilities, Familiars will probably gain Ability experience at a faster rate than their Maga, but this rule will 'cap out' once the familiar has learned everything the Maga knows. After this point, the Familiar has essentially gained an artificial 'season', similar to the seasons described in character generation of RoP:M, and will advance as any other Magic character, with no addition unbalancing benefits.
What do you guys think?