If you have these needs you should diversify processes in order to achieve maximum performance.
I had a similar problem and, like you said I separate the display part from the acquisition part but I used 2 PIC24 in CAN bus.
Since it is based on messages with identifier sent from one side and those who receive them reads only those that can process.With only a 3-wire bus you can connect more PIC and for a few bytes sent is fast and does not require overload because the CAN is managed in its own right and buffers.