Perhaps your basic approach is wrong. Grab a ladder instead of trying to dig an 8,000-foot-deep hole. You'll get to my level much, much faster.
As best I can tell, you've moved the goalposts. You are no longer claiming, "Certainly if she had received from and sent messages to foreign government officials on the State Department system, she would be 100% in the clear." Since the current State email system is not cleared for classified data either, it's no different legally than her personal server. Instead, you're suggesting a better approach that should be implemented, a future ideal world. I would agree, Uncle Sugar needs a realistic model for handling modern communications.
That has nothing to do with Clinton, however.
That's a whole lot of empty speculation. Based on the fact that State's email system has been hacked several times, and that IT experts with knowledge of State's systems say they're badly outdated, my speculation is that your speculation is a whole lot of wishful thinking. But yes, that's how it should be done.
I've always been able to see the difference. I do this stuff for a living, you know. It's one of the reasons why I said from the very start that Clinton's use of a personal email system was inappropriate. The point you keep dodging is it apparently wasn't illegal, in spite of the endless hand-waving, smoke-blowing, and often frankly stupid (Espionage Act of 1917?

) cries of the wing-nut propaganda machine. Endless speculation and innuendo presented as fact, eagerly guzzled by outrage junkies who love being played as fools.
Okay, let's try this one more time. Say for some bizarre, unknowable reason Mrs. Clinton decided to use the secure system that, well, everyone else in State uses.
Now let's say that Mrs. Clinton receives an email containing classified information. Can Mrs. Clinton be held legally liable for what someone else sent her?
(A) No, she has no responsibility for what someone else sends her.
(B) Yes, it's exactly the same thing 'cause reasons.
Assuming by some momentary lapse in judgment you actually said the obvious (and correct) answer, A, let us move on.
Assuming this scenario happens, the classified email message now resides on a State Department server. Is Mrs. Clinton responsible for that classified information residing on a non-classified server?
(A) No, she has no responsibility for the server - that's someone else's responsibility.
(B) Yes, it's exactly the same thing 'cause reasons.
Assuming that once again you actually said the obvious (and correct) answer, A, let us move on.
Let us assume, for whatever reason, that Mrs. Clinton decides to route all her email through a server in her basement, so the classified email now resides in her basement. Is Mrs. Clinton responsible for that classified information residing on a non-classified server?
(A) Yes, because she selected the server where she receives her email.
(B) No, she has no responsibility 'cause reasons.
The answer, once again, is A. By taking responsibility for the server, she takes responsibility for the email that server receives. This is not just a function of IT, it's ubiquitous in business. If a client sends me information I should not have - say, their firm's personnel files - to my business email account, it's not my problem. It's the client's problem for sending it, and it's my firm's responsibility to keep it secure even though we should never have had it. If instead I ask the client to send all correspondence to my home address and I receive those files, now it's my problem. It's still the client's problem for sending it, but now it's my problem because I'm the reason it is in that particular place and I now have the responsibility of keeping it secure.
Assuming of course that you disagree with this, let's move forward to her forwarding the classified email. If Mrs. Clinton forwards the email with classified information from her proper State account, she must select the security level. The purpose here is to keep classified and/or sensitive information from getting into the wrong hands, correct? Is this more or less secure than a system which treats classified emails exactly like emails containing the latest Dick Cheney joke or reception color scheme? If Mrs. Clinton replies to or forwards an email message through the State Department system, and she is following the proper procedure, then she is fine. If she replies to or forwards an email message through the State Department system, and she is following the proper procedure, then she is liable. But you don't get to assume that she automatically breaks the law and then claim that it's immaterial how she broke it so she did nothing wrong.
As far as "inappropriate", that's farting in a public pool or ordering white wine with steak.
EDIT: Just to be excruciatingly clear:
As I noted in an earlier post, had Mrs. Clinton received an email containing classified information on her official State Department, she saves that email as a record on ClassNet and then is able to legally send it to anyone legally allowed to receive it. That is after all why we paid for ClassNet.