Okay, gonna be brief
1:
Transmutation, level 9
Mass flesh to stone
Literally flesh to stone, but aoe.
Party friendly preferrably, medium-to-large aoe, medium range (or, samw range as flesh to stone)
2:
Transmutation, lvl 8
Mass baleful polymorph
Same deal as the above. Baleful polymorph but with medium-to-large aoe, and party friendly.
Adding these spells would give transmuters some options of aoe disable, and would make the school a bit more useful.