Your doing it wrong, you want the answers before you know the questions
First you should be listing your requirements:
Eg
What environmental conditions must the enclosure cope with
How much heat must it dissipate
Maximum weight and weight of components within
What should the cost ceiling be
i'm sure your capable of thinking up some more
etc etc
then tackle each question with answers and you should come up with a matrix sort
of cost/benefits etc etc.
And don't forget once you got all those, to search all avenues for ready-built/manufactured
items satisfying the solution before going to custom build
Then you can approach whomever is funding this for their input, etc etc