The new format FCOM's are based on the design of the A380 documentation ie. they're specifically designed for use electronically via an EFB.
Airbus have been struggling for some time to manage the vast amounts of data relating to the A320 family the format of which has not changed for decades and was managed by technology of a similar era. The only option available to them as aircraft get more and more complex (A380/A350) was to move to a new more managable electronic format (XML)
Unfortunately this means that they don't translate as well into paper format.
There is a cross reference table published by Airbus as part of the project. It's not in the FCOM though and it's down to the operator whether they want to distribute it. I'd say you're much better trying to learn the format rather than referring to a complicated cross reference table all the time!
Basically the FCOMs 1-4 have been divided up into the following volumes, each then subdivided by ATA chapter:
GEN/DSC (roughly equivalent to FCOM1)
ABN/NOR/SPO/SUP/LIM/OEB/FCB ( FCOM3 )
LOD/OPD/TOF/FPL/AEO/GOA/LDG/OEI (FCOM2)
The content of FCOM4 has been split between the above ie FMS function description in GEN/DSC. Abnormal procedures such as Dual Latch into ABN etc. Which in my opinion is very sensible!
As you point out the complication is getting your head around the page references. Because the FCOM is designed to be viewed on an EFB - when you view information on an EFB there is no such thing as a page. It's just a block of information - which Airbus have called a Documentary Unit.
Each Documentary Unit has an effectivity just like a page in the FCOM does now, and each section of the paper FCOM is built by stringing together the relevant Documentary Unit.
So if you look for example at the contents page for Abnormal and Emergency Procedures ATA 21 (PRO-ABN-21) you'll see that rather than being listed by page number they're listed with a corresponding letter. For example AIR PACK VALVE 1(2) FAULT.........................................B
Because the sections are made out of blocks (Documentary Units) which are as long as required to contain all the information needed for a procedure (imagine it being displayed on a screen with a scrollbar rather than on multiple pages), the size of the chapter, and therefore the page numbering are not tied to any particular piece of content.
Eg if you write down that AIR PACK VALVE 1(2) is PRO-ABN-21-Page 1, you might find that at the next revision it's moved to Page 4 because the procedure in front has suddenly changed to be 3 pages long. Instead of page numbering you'll find the letter B in the footer which will always correspond to the location of that particular procedure. So the correct reference is PRO-ABN-21-B which you can find quite easily just by looking at the footer.
Sometimes chapters have sub ATA's such as the example PRO-NOR-SRP-01-10 but again the system is logical once you understand it
There are some advantages! For example you can show page effectivities with aircraft registration rather than MSN, if you have more than one aircraft in your FCOM each procedure runs to it's conclusion before you find the start of the same procedure for a different aircraft (no more multiple page 1's etc).
That's my best attempt at an explanation!
Ulitmately if you don't like it, convince your rich owners to invest in an EFB
