Well, that sucks. That is much more complicated. Does Win8 have the reboot thing? I hope so.
You might be able to use the RunOnce key to Resume BitLocker on Windows 7 so that it can happen after the reboot has completed without requiring another action.
I haven’t fully tested this yet:
// Handle BitLocker Resume after reboot for Win7 and Win2008R2
if {version of operating system < "6.2.0.0"}
regset64 "[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce]" "ResumeBitLocker"="manage-bde -protectors -enable C:"
endif