I don't think I'd do it. Divine Favor and Righteous Might give significant bonuses to a fighter, and I have to wonder when they wouldn't want to cast it on a fighter.
The spells were designed with the cleric's lesser BAB and reliance on Wisdom in mind. Casting it on oneself presents a serious decision for the cleric. Casting it on a fighter is a no-brainer. Allowing them to do so would put a lot of pressure on a cleric to use it all the time.
Shield of Faith can already be cast on another creature, and as you can see from the design of the spell, it is much more limited than divine favor, giving only one type of defensive bonus, rather than the two offensive bonuses from DF.
You could adust DF and RM to be less powerful when cast on others, but it would be hard to do; you would have to make it less likely to be used all the time, but more desirable than a cure or other spell.
I have taken away heavy armor proficiency from clerics, but I haven't gone any further. I'm not sure what I would do to get the effect you're after.