beware of cross training to collect new techniques. i dont believe that a style or fighter is better just because he knows more ways to fight (long+short+medium range+grappling+boxing+etc). a fighter who is okay in many styles of fighting will probably lose to a guy who is really good at one.
since you are talking "fma", then keep in mind that the old masters cross trained by sparring with other fighters, and when they see something they wanted to be good at, they learned it. i will have to say the true fighters found a way to beat the guy who they lost to. its the only way you get better. you improve yourself, when you learn to find, make and take advantage of your opponents weakness, using what YOU are best at. not by learning what he did to beat you, because unless you drop what you are doing to specialize and master his art, he will always be better than you at his style.
i believe in the saying that you master the single stick by going to the single stick expert and specialize in his style. you master the single knife by going to the single knife expert and specialize in his style. but you master nothing when you go from one master to another.
now if we are talking about streetfighting, i still stick to mastering your method of fighting. a streetfighter does not bother trying to learn a little of everything. he takes what he knows and either he is the best at it against everybody, or he is not. you are better than that, as a martial arts fighter, because you dont settle with your skill level where it is, you should always work harder to get better at what you do. not what this guy does, and what that guy does, and bla blah blah.
so cross train? i dont think so. cross "spar"? yes. you are learning how this and that guy fights so you can beat him, not to collect his techniques. but if you truly want to adopt his style into yours, you will have to learn the true meaning of his style (not collect a few of his tricks), then specialize in that style as much as your own.
