Yes, yes there are countless threads on this topic already, but they've never answered the technical questions that every modder making a total conversion mod needs to know.

As we all know, 1.2 criteria are:
a) Roman faction must built an Imperial palace in Italy province
b) Post 220BC
c) 'Random' element

1) Eliminating the Marian Reforms event
Easiest way to do this is to stop an imperial palace being built in Italy, specifically by getting rid of the thing that marks it as Italy. Is this just the hidden resource or is it based on settlement/region names or RGB values?

Does the italy hidden resource have to exist somewhere or can it be ditched completely?

On a similar theme, what marks Rome as Rome for the purpose of victory conditions? Hidden resource, settlement name, province name or RGB value?

2) Altering the Marian Reforms
Once we determine the above, we can obviously move the physical location that the marian reforms can be launched from, but what about the timing element? Is the 220BC based on turns or on the date? If you have a starting date of 320BC, or are using 4 turns, will they become available in 270BC or do they stay fixed in 220BC?