The downside with using sukeul as a mobile unit you don't really gain anything to it in aro, same burst etc I used it in active but rarely mobile. Just try it and have fun :)
Kaeltars already have shotguns, and are specialists. They are perfect link fillers, and you have to put them somewhere anyway. So Sukeul ML's LS doesn't necessarily bring a new weapon to the triad.
The other upside is, your opponent is also at a reduced burst, and cannot just through smoke and MSV2 shoot you. I have found the Missile Launcher to be the most effective when I have left her out of sight until my turn, and then just blast away and some choice targets, and then go back to hiding until the turn 2 or 3. The BS 13 shotgun is pretty awesome for clearing things out when you need to. I have only done this a couple of times, but she cleaned house when I did.