Ah yes, great minds think alike, I had been thinking along the same lines.
The trouble is, when it is for a customer, you are reluctant to remove a safety item after IVA.
Of course the owner is free to do what they like, but you don't want to have to defend actions if someone is injured as a result.
VOSA did face legal action after a cobra replica owner suffered serious neck injuries in an accident due to the lack of a head rest. They were able to defend the action by showing the rest was fitted at the time of the IVA.
Similarly making your own hybrid version from different designs, however well engineered, will not have the same manufacturer guarantee to fall back on.
Struan