Personally, I think starting a unit is a great idea. It's also one requiring lots and lots of commitment — I would imagine that starting a SAR unit is really tough work.
You'd want to discuss your thoughts with whoever the local authority is who's presently tasked with SAR, and whose approval and support you'd definitely need for all kinds of reasons.
In the US, the local authority would be the county Sheriff, and our guy, who loves SAR. His backing is a tremendous asset.
In the US, there are major issues involving liability, so if you want to keep that in the back of your mind. As long as we're acting as agents of our Sheriff, we're covered. But if we are to free-lance, or do something that isn't approved (like sending someone unqualified or working beyond his skill level, into the field), we are subject to lawsuits.
Just FWIW.