Not sure, based on your description he should only be pitching. 6.55 and a strong arm are two tools that really stand out. Also, FWIW, power arms often develop into power hitters.
There is a 2016 by the name of Josh Lowe who we selected for our All American Game. He is a tall (6'4") RHP and throws in the mid 90s with a good breaking ball and change up. At the same time he is the #1 tools guy in his class. Plus runner, Plus Arm, Plus Field, Plus hitter, Plus Power.
He would be a first round pitcher, still might be, but we think a MLB club will draft him very early as a position player. We are very happy that no one turned him into a pitcher only.
He is just one of many examples.
Based on size, athleticism, and the two already obvious tools your son possesses, I think it would be wise to have him play a position. Zack Greinke was mostly a position player in his younger years and just pitched some. He was still drafted as a pitcher.
Guess I don't believe in kids that have plus tools becoming pitchers only, unless they are among the very best pitchers in the country.