Is is possible to customise OVA output options?

[hamishmarson]

When generating an OVA, the result often won't import into vcloud director due to issues requiring fixup using something like ovftool.
Is it possible to customise the OVF parameters included in the generated OVA? e.g. to

1. specify a different number of CPU's or Memory
2. Add one or more NIC's
3. Alter the HW defined. Max HW version etc.