I install hoods onto installed levers all the time.

I spray a little rubbing alcohol in the hood and on the lever, and the hoods slide right on from the front.

The ferrule then gets pushed down into place from above (again using a little alcohol to ease sliding into the hood's hollow tip) as the housing is being installed from above.

I was thinking it might not be easy removing/installing the lever from an installed, taped lever body.
Removing the pivot shaft requires removing the bolt that holds the lever body to the clamp, so much care would be needed to avoid disturbing the bar wrap.
Not saying it can't be done, it can be done, but could be a challenge to re-secure that mounting screw afterward.
Ok, if your tape has already been secured with finely-wrapped twine...

Turkey levers are the bomb. Pretend not to be a racer, yet race, if you're inclined, using turkey levers!
Just polish those turkey levers, they deserve it!

Auxilliary road brake levers were re-invented by a European cyclocross racer named Runkel (back in the '90's, I believe).
Production "interrupter" CX aux levers then hit the market so as to be compatible with integrated shifters.
But the traditional Weinmann/Dia-style "safety" levers still offer the simple, lightweight and lowest-cost solution while retaining so many bike's originality to a "T".
Here's my off-road-going Miyata Six-Ten, using the original Turkey levers with some Shimano hoods added on. I couldn't descend mountain bike trails without them!