kat, the problem with your suggestion is, that if one believes that there is only one God, then saying "may your god bless you" is, at best, as meaningless as "have a nice day". At worst, it actually contains, consciously or not, an implication that you will not be blessed, or even worse, that you will be unblessed.

I must admit, I see an attraction in using the phrase to Christians who have a deeply limited idea of God as a judgemental and punishing person, especially as, without knowing what I meant, they would find it offensive. It is an attraction I do not respond to. (I do allow myself to enjoy saying "God bless you" to priestly persons of denominations who believe that blessing is only possible if you are a priest, and male, but that is for a different reason.)

Someone who truly wants to invoke the divine in blessing, and believes in one god only, cannot do what you ask, though. It is not possible. Surely, if blessing is intended, then blessing can be received. (If what is intended is mere platitude, or worse, a religious point scoring, then your reaction is quite proper. No blessing intended, none received, and feeling put out. Do you tell them?)

Penny