I'm currently GMing a 6e game with three people, a "martial artist", a fairly weak blaster, and a super brick. Another player would like to join in (starting characters are "rookie level at 400/75) but his character concept is a Hero that can Multiform into four distinct "elemental forms". His plan is to do an Earth form, a Lightning form(air), a Fire form, and an Ice(water) form.
My Question Is: Is this too powerful? The versatility alone seems amazing, but I'm still a rookie GM myself. Is there anyway I can guide this characters creation without destroying his concept? Any thoughts are appreciated.