The questions seems to be CAN it be done and is it worthwhile.
The answer to the first one is surely yes. The US converted old Hellcats to cruise missiles in the Korean War, the US, UK and Germany did the same with bombers in the second and the Japanese used all manner of planes as cruise missiles, with minimum modifications(albiet with a guidance system rather more precious than any CPU).
The answer to the second question is dependent on the needs of the country involved.
If one has large numbers of obsolete supersonic fighter laying about and one foresees a need to launch missiles with heavy warheads at a big tough target in huge waves to exhaust the AAA missiles of an adversary then it might make sense. So for, say, China pondering US CV's in the Taiwan Straits, it might well make economic sense to load these up with bombs, fill the cockpit with torpex and store them in the event things turn hot.
For specialized attacks against hardened targets they might be useful as well, but the cost benefits are rather different for different countries. The US for instance would likely not stockpile old fighters for this (it has missiles sitting on the shelf) but it could be extemporized if needed (as it was in Korea).
