We’ll clearly have to agree to disagree on what the residual value would be.
The value is practical not monetary. To say you’d be left with nothing is a little extreme. What you would be left with is a more portable, quality (albeit old) amp. If that means that it is used more then to my mind it has been made better.
There are people who think that anyone spending more than one minute faffing with these old amps need their bumps feeling. However, fans of the marque and particularly of this era would recognise the value of rehousing the amp. Popping out and buying the lighter weight head only version is not that easy as they’re not exactly easy to come by. The OP could indeed leave it as is, untouched as a piece of history but very few people have the luxury of space required to have old 4x10 combos sitting dormant. To my mind if splitting means that it or at least part of it is going to be used more, it’s a no brainer.