Variants that help standard Chess skills

This is something that I have been curious about for a while now.

A few ideas I had which can easily be setup on something like Chessmaster against different levels of opponents....

A short-range variant: 1 King, 3-4 pawns and 2 Knights for each side.

Long-range variant: 1 King, 1 Queen, 2 rooks, 2 bishops and 1 pawn(optional to semi-protect the King on a thin board).

Once you get good at say the short-range games, then start slowly 'sprinkling' in the Rooks, Queens and Bishops one at a time.

These hypotheses I threw out here arent so much about winning/losing(especially the short-variant) but allows you to focus all of your thought towards fewer kinds of pieces at a time. As a newer player and 'chess remedial' I want to try some things like these to get more experience vs playing Blitz because becoming a good Blitz player is not my main goal in Chess at this time; Standard Chess is.

What Chess variations do you know of, if any, that could potentially assist as a decent skill-builder from a slightly different perspective/angle?

Rather than variants, I have favored endgames, which have the same sort of educating effect. But in teaching children, I have used some variants like king-and-8-pawns vs. king-and-8-pawns.