You guys just need to use macros. For example I am a dragoon. One of my main combos is:

Impulse Drive > Disembowel > Chaos Thrust

Instead of having the abilities on my bar taking up 3 spaces, I just made a macro:

/ac "Impulse Drive" <t>
/wait 3
/ac "Disembowel" <t>
/wait 3
/ac "Chaos Thrust" <t>
And added that macro to crossbar. Now I\\'m using only one button to use 3 skills. Just an FYI because like someone said, just because games like shooters utilize L2+R2 does not mean every game is capable of it. As it is the PS3s limited memory will not even allow us a keyboard and mouse interface.