You're idea is good, but probably not needed.
Go with the standard method as in your imgur drawing.
Make sure your 5V rail has a 5.1V zener on it.
Make sure your voltage regulator on the 5V rail has a reverse biased diode from output to input.
Also, if you are concerned that the "standard method" will cause the 5V rail to bounce up when the voltage exceeds the top diode Vmax+0.4, why aren't you also concerned that the "standard method" will cause the ground rail to bounce down when the voltage goes below the bottom diode Vmin-0.4V
i.e. ask yourself this: why are you satisfied with a diode D1 as the protection device for the negative excursions but you want active clamping for the positive excursions only? If you think the standard method top diode will pull the +5V rail above 5V, then why don't you also think the standard method bottom diode will similarily pull the ground rail down below ground??
i.e. why don't you also want active clamping on the negative excursions below ground?
see my attached drawing
I've given you a thought exercise here.
It also helps to think about this: how much current can the the INAMP supply above 5V or below ground?? in most cases, the usual standard clamping diodes do not cause the rails to rise or fall because the energy per clamping event x number of events per second = watts is less than the total power load of the rail, thus the loads will consume it and not allow the rail to rise (or ground to fall). Now, IF, in your case, the power load of the rail is much less than the power delivered by the INAMP, then you might have a problem that needs fixing.
^^^ I just drew this to get you to think about it, you likely don't need active clamping like this unless your load on the 5V rail is really, really low and /or the INAMP can supply excessive amounts of current. Think about the energy in W.s x seconds per event = watts .... and where it can go during an over-voltage event.. if the power exceeds the load power (consumed) it will raise the rail.. if not, it will not raise the rail, but will be clamped at the input to a diode drop below the rail.