Contract Offer: Option for a future extension?

I know Celtic do this often with their contracts, and I assume many other clubs do as well. I just offered a player a 5 month contract in my game to test him out without committing to a long contract (it's the winter transfer window). I was hoping to find a clause that would allow for an automatic extension of the contract for yae amount of time at any date in the future, but there isn't one. I think this would be a great edition in future versions of FM (or patches, if it's patchable, but I doubt that).

For 12 month deals for veterans, it's possible to have a 'One Year Extension After # Games' clause. But I can't remember off the top of my head if it's applicable for all contracts.

Actually a lot of players in Holland have contracts that have a one-sided (from club view) clause that allows the club to extend the contract with 1 or 2 years, so wouldnt mind being able to have such a clause in FM.