It sounds interesting, although it could swing the balance too much to the other side.
Yup. I'm definitely not saying that's not the case, but if anyone else tries it out I;d be very interested to hear how it works for you. Also worth pointing out that we only play with 4 players (sometimes even 5) so it never happens that a player has more fields than there is famine by the normal rules.
It's also worth mentioning as feedback that in our game Granary came out in the second round before the famine marker had started rising and so it had very little effect. It could well be that a Granary in round 3 or 4 would have suppressed the famine too much.
I think what I like most about it was how it gave players a bit more control as a concerted effort to remove events causing famine is now actually viable. Best of all, it made the Famine event much more serious which those without fields desperately wanted to stop, especially when it came out early [much like how everyone rallies round to nip Earthquake and Military Defeat in the bud]. In the past, the Famine always seemed pointless since Rome was always starving anyway.
Another variant I'd considered:
Add a third 'grain' symbol to the fields in the A deck. This way players who buy early fields will be much better protected, but it's still impossible to predict how many points this will save them overall.
I'd still be interested in trying this some time, but after yesterday's success we'll definitely be trying that some more.