Bridge utils only depends on net-bridging-KERNEL.tcz, which depends on ipv6-netfilter-KERNEL.tcz
Otherwise that's it. Works for me, but I build my own kernels.
The following modules should get loaded when you issue that addbr command.
Module Size Used by
bridge 163840 0
stp 16384 1 bridge
llc 16384 2 bridge,stp
ipv6 503808 17 bridge