For sure! They do love to burrow so I'd add at least a few inches of rubble rock/ larger grained sand.. if you start them off small and feed every couple days, you could also add a few medium sized fish (if you're going with a smasher). I have a pair of black occelaris in with my N.wennerae mantis and they are great together.. adding a group of hermits can help reduce aggression to fish in the tank (just know that eventually you'll have piles of broken hermit shells). I'm not aware of any mantis that isn't safe with coral, so keep that in mind when deciding on how to further stock it.. I'd go with easier soft corals and refrain from using higher intensity lights as these guys can get stressed from being in too much light.
With a 40 Breeder (150L) everything can be kept within, the biggest tank sizes I give for recommendation max out at 150L but it is suitable for Peacocks or Giant Spearers depending on how confident you are in keeping them and what your general preference is, I don't recommend Peacocks to first timers though.