That picture is from digimods.
All of that diagram was done digitally on a computer.
However it could be replicated, however the design and layout of the perspex and hinges mean it would need some design and engineering done first. It can be sealed, even if the seals fail the electronic boxes and cables can be sealed.
The carbon fibre part is fairly easy same as the perspex attachment, the hinges would be a problem getting them in the bay of an Astra.
Disadvantages are:
Carbon cracks are hard to repair
Carbon is expensive
Locking mechanism may be useless, due to top pivot
Doesnt improve looks.
You can buy other split bonnets else where btw, this bonnet would set you back about �8000 I reackon.