In Verbs^x, Indirect speech^x, Subjunctives^x

With all the wanderings of this thread, I am not sure of the question. Regarding these sentences: "i wish i could tell you what this is" (this present unidentifiable object) "i wish i could tell you what this was" (the same object) "i wish i could tell you how i feel"...

well not really you see this is not a case of subjunctive..as i said in my first postr (cite fowler here)...there is no sequence of moods in english... therefore, for example, we do not say "if i were to say i were happy" we say, instead, "if i were to say i was happy..." you...

i can't seem to find a hard-and-fast rule for a situation like this: "I wish I could say (that) I was happy" (if the speaker is attempting to express that he/she IS NOT HAPPY RIGHT NOW) would it be incorrect to express this as: "I wish I could say I'm happy".. one hears this sort of...