This is a good idea, but I suspect it's too complicated (or even impossible) to implement, or we would have some form of limited multi-attack in the game already.

As an alternative to something which makes multi-attack games really fun and more "realistic"/slow-paced, while keeping all the fun of multi-attack, I use a deployment limit. Check it out here:

https://www.warlight.net/Forum/82395-deployment-limits-easy-new-rule-implement

and one of the card options could be how many moves extra the card should give; 1,2,3,4,5,6,7,8,9 or more.

another thing to be sorted out is if the card should give total amount of how many spots all your armies could take, or if it should be restricted to 1 army having to use the extra moves alone

I think maybe a shorter multi-atytack would solve some problems. I hate having someone able to run through 8 stataes with a big stack (although it is usually easy to clean up) and disrupt the game in a fashion that is not relaistic; however, having a multi-attack option that allowed say up to 3 or fours spaces a turn only would not be as disruptive and more realistic. I like the idea of having a crad to trigger this option.

please check other card ideas at http://warlight.uservoice.com/users/15429559-gilgamesz

I also love Avalon Hill's Blitzkreig.

I don't know how well this would work out exactly.. but I do agree with the idea behind this.. I've always wanted a play style similar to the blitzkreig game, with a restricted multi-attack system.