Apparently Mourinhos last contract with Chelsea had a clause in that the club would continue to pay him (weekly or monthly) until he found another club, instead of 1 big payout, which is why he took his time. Seems like a sensible option, however I'm not sure we're a big enough club to attract big managers and get them to agree to a similar clause.
I'm assuming Chelsea must have that with all their managers considering the amount they go through.
Yes the definitely did with Di Matteo. He won the CL got a big contract with them something like 7m per year and the clause was they would pay his wages in full until the end of the contract in 2 years unless he took another job. So he turned down job after job until they had paid him up in full then took the Schalke job not long after.