On a plate mounted KB you cant really do that because the legs have no where to go when you try to bend them to pop open the top.
People usually resort in re-soldering the switches and I find that very too high-risk for my liking.
But what if you could just basically cut certain spots something like that:

and remove the top off. Then basically gut out the switch by fishing out the remaining legs and when you are done with replacing the spring/stem/what have you, just take a new top of a donor switch and done.
Could this work or am I missing something?
Obviously its sort of a destruction method but hey, if it gets the job done...
Any ideas?