Well now that a little more information about this job has been forthcoming, I will weigh in.
This kind of project is our specialty and we do it all the time.
First of all, I would absolutely subcontract having the moulding chopped and the acrylic cut to size by an outside resource.
The advice that it will eliminate your profits is unfounded. Regal Piedmont (a major plastics supplier) has $100,000 beam saws in several of their locations. We buy the acrylic from them, give them a cut list which they plug into a cutting optimiser, and for $60 per hour, cut, label and stack the acrylic. And they deliver it. We pay our standard costs on the acrylic and then $60 per hour on top just for the cutting, and it is much more accurate than score and snap.
I would recommend using film masked acrylic as opposed to paper masked. (And don't let anyone tell you that blue masked acrylic is an inferior product). While you may have to replace a piece or two due to scratches, the labor saving of unmasking the acrylic with film masked will more than offset the cost of replacing a sheet or two, Also, there is much less static generated with film masked. I would stay away from Plaskolite and stick with Cyro FF. We just finished a job with Plaskolite and it is definitely an inferior product and it has way too many surface flaws. Both are ACRYLIC. I would not use anything thinner than .098. We use .118 and feel it is worth the extra money.
RE: bulk chop: We have dedicated double mitre saws but still order bulk chop in many situations. Often you can negotiate getting chops for about what you would pay for length, and for a small shop, there is no way I would recommend cutting your own. You don't say how large the pieces are, but I would recommend using snap in hangers to save time.
RE: mounting: We use a Potdevin NTZ gluer and I would think that a job of this size would more than pay for the machine. Better yet, can you find someone in your city that has one and subcontract the mounting as well? Check under "die cutting" in the phone book. Most die cutters or printing finishes have a Potdevin Machine. Speedmount (or an equivalent) product would be suitable but it is significantly more expensive and very slow. We can mount 100 24 x 36 posters per hour with our Potdevin Machine. I don't know what size press you have, but even running two at a time, have you calculated how much time it will take to mount? You don't say what the profile is of the metal frame, but if it is #5 or #11, 3/16" fome core plus acrylic will make for a slower fit because it will be harder to get the springs in. 1/8" fome core (even speed mount has it) will make for a faster job.
And finally, has anyone calculated how much space even 100 finished pieces takes up let alone 1200? Moving them around the shop? How to get them to the client? Even if they are picking them up, who takes them to their vehicle? What if they aren't "ready" to receive them and you have finished. Is your shop big enough to store them? How are they being packaged?
If you can give more specifics about the job, I'll try to help with other pointers.