Whats wrong with oil?
I don't have experience with diamond mill tooling, but I understood that no oil is only for dealing with super alloys. Super alloys when machined by diamond experience a red hot surface temperature, i.e. the endmill is red hot... in this situation the oil would likely burn and stick to the tool. Are you sure they are not just saying that no oil policy incase you decide to stick a sheet of inconel on the machine?
I like to use diamond bladed saws though, for angle grinders and chop saws. I put a 14 inch diamond blade on a chop saw and I cut through a 4x3 inch solid aluminum block to make plate slices. When I cut, I spray it down with wd40 as its cutting. If I don't spray it with wd40, the diamonds get clogged. If you need to cut aluminum on a diamond chop saw (and I mean the metal cutting diamonds, not the tile cutters), just keep it sprayed on... and I am pretty sure I did some cuts with silicone WD40 and there was no problems either.
When I did comparisons with carbide endmills on aluminum (freshly acetylene oxygen gas welded soft stuff), I found that regular wd40 works well. I tried to use alumitap from tap magic, which is what I use for tapping... anyway alumitap makes the endmill clog, I suppose its only good for low speed work with a tap. So long I kept spraying wd40 fairly frequently I managed to machine a great deal of aluminum weld without any clogs. Again, it works fine for diamond angle grinder / chop saw blades too. Go figure huh? regular old wd40 beating out the aluminum product of choice... but again this is for diamonds and high speeds, NOT tapping. I use alumitap for aluminum tapping.
For aluminum die grinding I use the alumicut large flute burr with wd40, and for aluminum milling I use a 3 flute non ferrous metal carbide alcro endmill with again..wd40. wd40 smells alot better then tap magic too (what is in that, menthol derivatives? )
I think you should stick with oil and get a wash cabinet to clean up the metal after machining. You will also get less dust if you use a coolant, which is good for your lungs. I don't think spraying alcohol is a good idea, it has a low flash point compared to normal oils. I would say that its actually a really bad idea. Your work piece is gigantic plate, cover that with alcohol and its like a truck fire. Alcohol is fine for small shop use probobly.. but not for a giant plate machining operation. You are talking 6x4 meters, thats 18x12 feet. That would make a hell of a fire.
All it would take is a inclusion into the aluminum sheet to spark against the endmill and light it up. Or maybe a diamond from the endmill getting separated from the endmill, lodging into the sheet, and then being sparked by the next diamond in line (sinter fail).