I'm not sure what in you description is not doable with Situations - except the dampening part (at least for now, they are on TODO also but a bit further down on the list). Probably it's just a question of different mindset / mental model on how the application works.

Situations model is more about states than enter & exit events. That is, if you configure a situation with some settings, those settings will be active during the situation and be automatically reverted back when the situation ends (there are of course some exceptions with actions that cannot be reverted reliably/easily or at all, like launching an app). And then there is of course the normal phone state when no situation is active.

So, if you want to have wifi disabled and mobile data enabled by default, first make sure you don't have any situation active (just to make sure situations is not already in some state for those settings) and configure your phone settings like you want them to be. Then create situations for different locations and make them enable wifi and disable mobile data. This way you will have wifi on and mobile data off in those locations and elsewhere vice versa.

So you don't necessarily need a baseline situation since your normal phone settings are the baseline.

Does this make any sense?