It seems I have a bit of free time now to take care about some FreeBSD related things.
As part of this I already committed the UFS/FFS related FEATURE macros which where developed by kibab@ during the Google Summer of Code 2010. The network/ALTQ related FEATURE macros are in the hands of bz@, he already reviewed them and wants to commit them (with some changes) as part of his improvements of parts of the network related code.
The GEOM related FEATURE macros I just send some minutes ago to geom@ for review. All the rest went out to hackers@ for review. The rest in this case is related to AUDIT, CAM, IPC, KTR, MAC, NFS, NTP, PMC, SYSV and a few other things.
If everything is committed, it should look a bit like this if queried from userland (not all features are shown, those are just the ones which are enabled in the kernel in one of my machines):
kern.features.scbus: 1
kern.features.geom_vol: 1
kern.features.geom_part_bsd: 1
kern.features.geom_part_ebr_compat: 1
kern.features.geom_part_ebr: 1
kern.features.geom_part_mbr: 1
kern.features.kposix_priority_scheduling: 1
kern.features.kdtrace_hooks: 1
kern.features.ktrace: 1
kern.features.invariant_support: 1
kern.features.compat_freebsd7: 1
kern.features.compat_freebsd6: 1
kern.features.pps_sync: 1
kern.features.stack: 1
kern.features.sysv_msg: 1
kern.features.sysv_sem: 1
kern.features.sysv_shm: 1
kern.features.posix_shm: 1
kern.features.ffs_snapshot: 1
kern.features.softupdates: 1
kern.features.ufs_acl: 1