I like DBArtisan from Embaradero for DB admin work, and it will generate change scripts, but it is not anywhere near the capability of BMC Change Manager for DB2 z/OS IMO. Embaradero has another product that manages changes, but I have not used it.
I have also used the Quest tools, which are better at monitoring than they are at DB Administration (spotlight and foglight), although they do have an admin tool and it is improving.
DB2 Control Center uses the IBM supplied stored procedure to do changes not supported by native SQL alter (those which require export of data, drop table, create table, and load of table). You can see it in action by making a change and looking at "Show SQL" before you run it.
I would contact the vendors and ask for a demo, or just download the software for a free trial.