With the likes of the Storm Ravens, Wolf Scouts and a myriad of other Chapters and Deathwatches own moduis operandi of doing things a little different at times.. has anyone put together any "Stealth/Assasination/Recon" Oaths ..or.. do any exist already ?

I can't recall any off the top of my head. In any case, oaths must be taken as a killteam. A wolf scout couldn't simply swear their own oath for example. That said, killteams do go on stealth missions and it makes sense that an oath asking the Emperor to help keep them hidden would exist.

I'd consider this kinda interesting, at least on paper:

Storm Ravens

Raptors

Space Wolves Scouts

All take Kill Marine Advanced Specialty

Make an Oath for the GM that reflects some kind of effect that sensibly redirects the enemy at crucial points (one reroll per player, on the first failed roll on said mission involving stealth, recon, or avoiding notice.)

Could prove very interesting indeed.