I think that turkey just wants to create a buffer south of its border.....
I believe you're right. Turkey backed ISIS and other groups to try and overthrow Assad but the payoff was never what they expected. If they're no longer backing the terrorists, it's reasonable to have a buffer zone of sorts where the Turks can hopefully target terrorists before they come for revenge within Turkey over the Turks ceasing to support them. Turkey would recognize a lot of people Assad's folks might not so it helps Assad, too.
I think both Putin and Assad would go along with this as long as Turkey is willing to accept some pullback date in the not too distant future and promise to coordinate actions with Syria and Russia. Syria can still use all the help they can get and playing the anvil is easier and less lethal to your own forces than playing the hammer. Russia is clearly going to stand with Assad so as long as Turkey plays nice with Assad, I believe they'll agree to any kind of arrangement that Assad agrees to.
Whether any arrangement exists or not probably won't be in the news unlike the now popular US practice of insisting that private talks between leaders be published for the media Mad Hatters to twist and torture.
JMHo