Credant's full-disk encryption products do work inside a VMware VM, but one of the aims of Credant's software is to ensure that the hard disk is only ever booted on the one system, and it is extremely sensitive and will go into key recovery mode at the faintest hint of any change to the hardware visible to the VM. There are plenty of situations where you will need to decrypt the drive(s) before a change to avoid key recovery mode. (You can re-encrypt afterwards.)
Many of the host CPU's capabilities are visible to the VM, so a move to a host with a different CPU can trigger key recovery (although that might be considered a feature, given the nature of the product!). It will also sometimes be triggered by updates to Fusion (or being moved to a host with a different Fusion version), since new Fusion versions often include a new BIOS, and that sometimes makes Credant think it might be a different system. It could conceivably also be triggered by changes to the VM configuration (changing the number of processor cores or the amount of memory), although I haven't verified that.
In short: It should work, but don't expect it to be trouble-free. Certainly be prepared to perform key recovery when needed.
Good luck!
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Darius