Hm, the class seems a bit bland. Its essentially a bard like spell caster with marshal auras and a summonable minion.
For the bonded creature can the Legion Magus ever switch what creature it is? At level 8 it can only select a cr 6 creature and it seems like it only advances by racial HD or class levels. At say level 16 could the Legion Magus preform some ritual to bind a new summon with CR 16? Say a Planetar?