After several games, I have come to the conclusion that changing the movement to "roll 2 D6 and choose" makes for a very streamlined game. Essentially everyone has access to the yellow threat card "Navigator".
This lowers game time dramatically. Games with 2 players take up to 2hrs from start to finish with scenario endings. By 1hr of gameplay, players have at least 1 relic if not 2 and are moving in the middle tier.
It means you have less of that unpredictability that a regular D6 would give, but all in all, the players preferred this option.
What happens on a double? Nothing. you just move the roll indicated. That way the movement rule is easy to remember for everyone.
With 3 players, this change makes a big difference to the game. No more players b$$ching about not being able to land on a space to finish a mission for many turns. Herego, players are happier, the mood around the table is better, everyone has fun.