1. Select a town → space → Town Specialization.
1, 2. Specialization for Archangels:

function AddArchangelsSpecialization()
	if GetObjectDwellingCreatures('town_name', CREATURE_ANGEL) ~= -1 then
		local add = 1
		if grail_built == 1 then
			add = add + 3
		end
		SetObjectDwellingCreatures('town_name', CREATURE_ANGEL, GetObjectDwellingCreatures('town_name', CREATURE_ANGEL) + add)
	end
end

function NewDay()
	-- ... --
	if GetDate(DAY_OF_WEEK) == 1 then
		AddArchangelsSpecialization()
	end
	-- ... --
end

Trigger(NEW_DAY_TRIGGER, 'NewDay')

grail_built = 0

function WaitForBuildGrail()
	while GetTownBuildingLevel('town_name', ID_BUILDING_TEARS_OF_ASHA) == 0 do
		sleep(10)
	end
	grail_built = 1
end

startThread(WaitForBuildGrail)

You can also add the appearance of [Arch]angels on the map, but nothing can be done about the interface.