A sweeper with the bag removed might flip the grass up on top to accomplish your goal. Have you tried high lift bagger blades? I have a set on my L130 and they seem to create a lot of draft. I have also used a pine straw rake with some success too, the clippings are too short to collect but it does what you would want which is leave the clippings on top of the grass.
Either this idea of the sweeper without the bag or put a dethatcher on the front end (I know you said 3 point). Using a dethatcher on the 3 pt will work OK but you either have to mow the same path twice or wait till the next time you mow to chop them up.
If you put it on the front, it will bring up the clippings and you'll mow right over them.