Low cost ways of working with aluminium for a n00b

[Doddy]

Interesting. This is where, if you wanted to, you could sink an awful lot of money.

I might agree with you to an extent about the use of flat sheets of ali. You may want to research two finishing technologies that may go hand in hand with what you're trying to do - "shot peening" and "anodising", particularly if this is going to be an aesthetic piece. This is likely work you'd want to farm out once you have your panels cut. Your point of making a skeleton and bolting the plates to this does offer an easy-out for this, and you can get the Ali sheets guillotined reasonably accurately by most metal suppliers. Add your holes, then erase your markings with the peening process and hard-anodise to get a durable and sexy finish.

Widening holes is easy (files, etc). It's filling them in afterwards that's trickier. Get everything fitting properly before looking at the finishing processes.