Board Thread:Theories and Speculation/@comment-31338621-20190501030435/@comment-26636534-20190502230159

It's interesting to note what the added ability to his rasengan could have been regarding his elemental nature. With Minato's fighting style and jutsu in mind, it's clear he lacks a ranged technique and some defensive technique. The latter jutsu doesn't seem to be of concern to Minato, but for versatility it would seem as an option.

So, If we assume Minato would have combined the rasengan with each of his natures:

Rasengan + Fire release == powerful ranged jutsu.

Rasengan + Wind release == powerful defensive jutsu.

Rasengan + Lightning release == powerful close range speed related jutsu.

Just my own speculation here, but we saw how powerful the Rasenshuriken was. It stands to reason with the highest levels of shape and nature transformation, techniques of similar power are possible.