Something I read awhile ago, not sure where so take it with a grain of salt:
During season 3 Patrick Stewart was actually considering not renewing his contract. Having him become a Borg in the 2 part episode "The Best of Both Worlds" was something of a Soap Opera Coma moment while they deliberated. Had the contract renewal not occurred Picard would have been either written off the show entirely or else given an irregular role as Locutus and thereby becoming a recurring villain.
However, Stweard did decide to renew his conrtact as TNG was providing a steady paycheck and leaving the show to pursue potential prostpects could have bitten him in the ass financially.
One thing that was considered was giving Picard a permanent Borg prosthetic, specifically I think they mentioned the right arm, to leave a visible reminder of the incident. They ended up scrapping that too.