They could just block those in competitive server and leave it unlocked for movement-related gameplay like KZ/autobho/surf. Imagine how many people would be playing it. Coming from a movement veteran, that would be a fucking blast since Source movement mechanics are utter garbage. Source games still have the same bugs as 1.6, except for the crouch-running, which is called Ground Strafe or a variant called Standup Ground Strafe, or simply, SGS. You still do edgebugs, jumpbugs, ramp bugs (wall bugs), and slide bugs (I think?) in Source games like CSGO. They were never eliminated, they are just less frequent. If they don't want to implement a new engine, which is uderstandable, they could just port 1.6 to the Source engine like Kreedz Climbing developers did on Steam, I highly recommend checking it out, it's a free KZ/surf/autobhop game using 1.6 mechanics in Source engine. You don't have idea how many people, that are active only in CSGO nowadays, miss the movement of 1.6 and the unique feel it has. I still play 1.6 daily because of that. Imagine bringing the best of 1.6 to something new?!?! The best from both worlds, it's a win-win situation for Valve and everyone playing the game.