First of all your trick only works once, if the 4 BTC come from a transaction output that is sufficiently aged. So it's not "free", you're consuming the limited resource (old coins in this case). You could not, for example, use the same 4 BTC again to combine another single satoshi input for "free".
Yes, that's the currently agreed ruleset. So what's the problem again?
You've gone from saying they can't be spent, to they can't be spent for 6 hours? Come on. And not every bet is a losing bet. And you can spend 3 or 4 satoshis at a time.
Second, assuming that you did not have aged coins you would have to pay a fee. The 36 bytes for the additional input (the 1 satoshi) will drive the fee up by more than one satoshi. This is what we mean by "economically unviable to spend."
No, you can easily get a total of combined inputs and outputs of 6 or more without raising the cost from free. Have you looked at what's happening in the actual blockchain, or the logic for free transactions? And if you're paying the 0.0005 "minimum" anyway you can get away with a lot more inputs and outputs.