Where is your higher accuracy required; bolt hole size and location or in other places on the parts? I suggest you look at using both laser/waterjet and vertical mill. Cutting parts directly out of a sheet of 3/4" material on a mill is going to be slow and as you realise workholding will be difficult. You may find it best to get them cut with a machining allowance and then finish them to the precision you need on the mill. This allows you to solve your workholding problem because you have bolts holes available. If the bolt hole size and location tolerance can be met by the cutting method you probably need only one fixturing for the final machining. If the bolt holes need to be brought to tolerance you will just need to have a stop in the machining program and use only some of the bolt holes for fixturing with the program working on the unused ones.