Cyrus is my favorite War player, Mansa Mansa is my favorite builder type. Cyrus is good early game, but I've played him lots of times without ever having horses early enough to get immortals. I could even do without the apocathery, Persians play on good traits for the most part. Late game, especailly on larger maps, L6-8 units from you're West Point city is not an unreasonable goal. Though I tend to run Vassalage and Theocracy all game with him.
As for upkeep, founding 1 new city running a high maintainence civic early game (Orginized Religon) and Monarchy, low upkeep, adds 1 pop and 1 city, so it saves .8(City)+.24(Pop)/2, .52, so yes, .3 was a low guess, but that is the Deity level cost increase, Monarch isnt much difference, .5 savings. Overall though 5.6 city + 8.4 Pop would amount to a solid civics cost of 14, like you said, and 12.6 on Monarch level, and save you a good 6 gold per turn. Yeah, that would pay maintianence on that 8th city pretty well unless it was extremly far away. I concede that it would allow another settler at that point, very good argument.
Alright, I'll add Orginized to middle teir in my view, that wipes out the lowest teir entirely. I'll say every trait is extremely good except Protective, Orginized, Industrious, and Expansive, and those four are very very good.