Absolutely. Create an event with the "Boss" modifier, and destroying it will end a level, and a boss health bar will appear on the screen whenever it's nearby. (You'll need to set up the Devan's head animation at the top of the bar, since non-guardian levels don't come with it. Do what I do, open up a guardian level, write down everything about the animation, and recreate it from scratch.) You can then use pretty much any behavior, just like any other event. It might not work so well with the behaviors that don't actually generate sprites, like some of the wind/tube stuff, but why would you want it to?

If you're thinking about the behaviors used by the actual bosses in JJ1, they tend not to be incredibly customizable. Pretty near all of them make reference to a certain row or column within the level, so it's hard to put them anywhere but the upper left corner, and some even reference hardcoded animation numbers. The Medivo guardian is actually pretty good... it does have to be above a certain row, but other than that you're allowed to meddle with a good number of its settings, including the space that it travels around in during its first phase. The Megairbase guardian is pretty similar to Float L/R but I guess it has that secondary rock-throwing attack if you can figure out how to get that to work. Most of the rest are just hard to work with.