Converting a old jets into a dumb target drones or kamikaze cruise missiles is relatively easy. Israel has done in wars, used old converted jets to force Arabs to reveal SAM locations, or redirect fighters and expend missiles. So the idea has merit.Nah, we need to look at what any potential adversary has and build/buy to counter that threat. Nobbling old planes is not a good idea no matter how cheap and tempting it is. We need to send the old planes to the aircraft museum and build to our own requirements the most advance drones possible. Hyper speed ,hyper height and outer space. When the mind has a focus anything is possible.
Another factor in PAF favor is while for most other airforces the maintenance is done by subcontractors making fielding old jets unfeasible as labor cost alone stacks up huge bills, PAF owns Kamra and the staff is in its own payroll so can maintain them indefinitely till parts available.
For UCAV role we can invest in new platforms as you said.