> Deep informal connections between both "sides" might substitute rule of law to some degree

It's a poor substitute. To the point that I think single-party rule may be preferable. Informal power sharing arrangements almost deterministically go to shit after a single generation. They also calcify the elites' ranks.

I might agree with you that it might be risky but I think exchange of top formal power every few years could keep unseen connections fresh and intergenerational.