I'm sorry but I do not believe Ricochet has any place in this game aside from possibly in S&D. It is Hardcore, so if I shoot a teammate I have to live with ruining his streak, making him mad, and running the risk of him coming back and ending my streak. It sucks and I don't like it, but that's the result of me killing the teammate (intentional or not).
I personally think that Ricochet was put in to prevent intentional team killing, but unfortunately I don't think most team killing is actually intentional. It is you shooting at a guy and a teammate runs in front of you. You throw a grenade and a teammate then jumps out the window right by it (or you have bad aim). You shoot at a character that doesn't have a name over his head (typically an enemy) only to find out it was a teammate. Adding in Ricochet will not change my habits any more. I'm still going to shoot those people or throw those grenades because my goal is to kill the enemy and it is unfortunate that the teammate got in the way.
I disagree, though I understand where you are coming from.
To me Hardcore should be just that: Hard Core. There should be no hand-holding. Friendly Fire should be on. Players should have to make wise decisions about what Kill/Scorestreaks, as well as what equipment they use. It should be on the PLAYER to make wise decisions.
The only Feasible change to scorestreaks I can think of would be to add a "Danger Close" element to them. (Not referring to the MW2 perk, but the Military use of the term). Meaning, basically, that if a Friendly is in the vicinity, the streak will not fire upon the enemy. If a teammate runs into ordinance that had already been fired, well that is on that teammate for not being aware. So for example... if you have a Chopper out. If a friendly is within a certain range of an enemy, the pilot will call off that strafing run or hold fire for Danger Close, similar to what is done in a military setting. Chopper gunners don't unleash into an area where there are known friendlies.
Beyond that, however, the player needs to be accountable for their own actions.
A "TKing" report needs to be added into the game, and players who abuse the system should be banned from HC modes.