The current battle regimen system is not very interesting.

Although it is true that combining certain attacks produces different effects, they are mostly similiar and there is little strategy. Most people tend to queue whatever attack they have next and just hope for the best. It's also difficult to see any significant results from using a battle regimen and some people in my linkshell have expressed that they feel it is a waste of time.

I think it would therefore be a good idea if you could rework the battle regimen system and add in "combination attacks". This would be somewhat similiar to Dual Techs/Triple Techs in Chrono Trigger. As an example, let's say we had the following combination attack: "Ice Sword" where the formula would be:

1) Any Blizzard-type spell.
2) Heavy Slash.

When both attacks are queued this way and the "G" key is pressed, you would get a unique attack where the Blizzard caster would imbue the other person's weapon with Ice and he would then attack. This might be useful in the sense that it would add the enmity directly onto the second person instead of the first, and it might count as a physical type attack against monsters with high magic resistances.

I believe that this would enhance party play, reward teamwork and give the impression of gestalt (The whole being greater than the sum of its parts). As each combination would have specific requirements, there would be less confusion about whether "I should or should not join in" the Battle Regimen. Not to mention: This is fairly original as far as MMOs go (at least until Guild Wars 2 releases, as that seems to be planning something similiar)

Unfortunately, this wouldn't work too well for friendly combinations. For example, you couldn't make a spell like "Barwatera" (Increases resistance to water) by using the combination Shell + Water spell because we are currently unable to use non-offensive effects in the Battle Regimen system.