I fundamentally agree with having pitches move. My question would be around something like 10u tournament ball. Lets say you simply want to spot a high-inside "fastball". Would you suggest throwing something different at that age, assuming you want to hit that spot?
10u, worry about location, location, location. Breaking pitches are pointless at 10u. If you want a riseball, just throw some high heat. If you want a curveball, just throw some outside corner heat. Drop ball? Yep, low heat.