I don't see the problem with a young player making more than the ten-year guy because in the real working world, the next generation of worker tends to make more more than the past generation (all things being equal). However, a rookie cap isn't a bad idea. Let them earn their big payday in the pros.
As for the minor league pay, it's not great but players know this when they choose this profession. As somebody previouisly mentioned, it's like an internship to play in the big leagues so there's no feeling sorry for anybody. Nobody's twisting their arms to get into this business. There are people who intern for nothing in their chosen field so minor league baseball players don't have it bad at all.