Speaking with Valkyria Chronicles producer Kei Mikami at E3, he revealed that Valkyria Chronicles 4’s new class, the Grenadier, was actually inspired by a bug they found during the development of the first game.
Apparently toward the end of development, a bug would pop up that caused your squad’s tanks to shoot grenades instead of shells. While they were able to fix the bug, the team actually enjoyed this long range grenade style of play.
They even wanted to add it as a new class in the first Valkyria Chronicles, but unfortunately it was too late in development to make that large of a change and the idea had to be scrapped. They tried to bring it back for the second Valkyria Chronicles, but couldn’t make it work there either.
Source: IGN.com Valkyria Chronicles 4’s New Class Came From a Bug In the First Game