There seems to be a lot of confusion surrounding not only what the OP wants accomplished, but also what is possible to accomplish. I have not worked with PSA before, nor have I done any model swapping, but based off of what I've seen others accomplish, this is what you should do to achieve your goal:
1) Swap the pikmin models for the models of the items you wish them to be.
2) Alter the moveset so that when you want Toad to use an item the game checks what kind of item (pikmin) is first in line, destroys that pikmin, and generates the corresponding item.
Generating items to use in movesets is nothing special and pikmin model swapping isn't really new either, so the only place you may have a problem is in determining what item to spawn when certain pikmin are first in line. I can't image why it would be more difficult than a few simple if statements, but I do not know if PSA can give you access to the needed information about the order of the pikmin (seems likely that it should be able to, though).
As was already suggested, if you truly intend to put the proper time and effort into creating a moveset, you should get in contact with SDo0m InCaRnAti0n (the maker of the Shadow PSA that spawns items). Sdoom is probably the most knowledgeable PSA'er in this community. Try not to be annoying by expecting him to do too much for you--if he is willing to be a source of information his help will be invaluable so you don't want to chase him off
Best of luck with your project
