Don't use the base with the color of your gamepieces but the one direct opposite to it as your starting point. This means green starts from the blue base, red from yellow and so on. Then you need a coin to determine positive and negative movement. Your goal is to get into your House, but your game pieces are moving forward and backwards now! All other rules apply as normal.
Why don't you just choose whether you want to move forward or backward, instead of using the coin?
This variant is very nice. The only problem I see is when you play with 3 people instead of 4: one of the players has a worse situation than the other 2.