If I'm understanding you correctly, this is already done and will be in 3.2. There will now be "profiles" for buy-ins, rebuys, and add-ons. To take buying in as an example, at buy-in you can select which profile to use. Each profile has its own Fee, Chips, Rake, etc. Of course, you can still customize the values for each individual buy-in (at the time of buy-in), or you can select a pre-defined buy-in [profile]. Basically, by selecting a profile, all of the values will be filled in for you. Makes it easy to switch between known sets of values.
See attached screenshots of the updated Game tab, the dialog for managing profiles, and the Add Players dialog.