The widget scaling system can easily map to a midi value by entering the value using an “m” suffix e.g. entering 7m will convert to the equivalent of midi value 7.
When using radio buttons for this, you also need to disable the setting in the Value tab of the widget properties to send a value when the radio button is in the Off state (otherwise each button will select the first snapshot when switched off).
Were you aware that there is an automation parameter in Native for the snapshot selection? So you can use this instead of sending midi.
Also, there is a great user gig file template for Native that has the snapshot selection already set up.