Marian Reforms revisited

Okay, so we know MR are bound to the 'Imperial Palace' building. But, what exactly about this building makes it happen?

Four possibilities, in order or probability:
1. the place in building queue. Most probably... the last building in the core_building tree?

2. capability 'recruit roman praetorian cohort i'

3. the name. Just the name of the building 'imperial_palace' is enough.

4. capability 'upgrade_bodyguard 1' for all factions

Anyone has tried any of these?

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How to bind Marian Reforms to specific event:
- A city conquered:
imperial_palace requires hidden_resource province and not factions { provinceowner, }
This way only after the city falls to the enemy can an Imperial Palace be built. Set the construction to 1, to make the effects as soon as possible.

- specific date (more or less):
okay, before the patch comes out, this will require wasting a faction, so make it a 'Senate' faction, but it must be well protected from any attack, and have lots of cash on startup.
Single province. Allow this faction to build ONLY the core_building. Give the starting city a 'huge city' level and all core_buildings except Imperial Palace. Set the construction time for Imperial Palace for desired number of turns, and give it some VERY significant bonuses, so that AI would be convinced it has to build it.

Both ideas not tested...

Any more ideas?