This is great for producing GS's, but when u place National Epic in a city, that means you consider that to be your main GP farm, and in those cases you want another type of GP, you will struggle getting them with all the pollution.
I have won games, never ever producing a Great Person except getting them from Techs. GS are generally the most useful and Powerful Great Person available that is easy to acquire.
This sounds like an overkill to me. With Ironworks and Heroic Epic alone, you are already producing a military unit every, or every second turn anyway. I'd rather split them up to have 2 great military cities.
But both of your suggestions sound fun to try out, and they might be more effective than i think
This is at the cost of not using WP either, But In that Strategy I emphasize quantity more then quality
I've Produced armies so fast using the HE & IW combination that I had to switch the city to build gold to cover the cost of my military units, that or switch to Vassalage if I'm Spiritual, I Generally like using this strategy with Isabella.
Shrines allow you to assign an extra 3 Priest, so with Angkor Wat, and any Extra Great Prophet Settled, you get a production monster. I Once was using this strategy and and ended up with 3 Holy Religions in my capital, half way through the game I realized that my shrines and settled Great Prophets had accumulated 50+ Gold all together and decided to go for a HE & Wall Street Combination instead.
50gold + Bank, Market, Grocer and Wall Street is an Extra 150 Gold
Now it was a wealthy Military Production center that could also the cost of war
Another possibility using Angkor Wat, is the HE & NE combination.... I know I know... it has no synergy, well... actually it does especially with Angkor Wat. Each Priest you assign gives you 2 Hammers, with HE it become 4H for every Unit you Produce, and while your Priest are assigned they give you GPP towards another Great Prophet which will eventually be settled for another 2 Hammers, It's just a cycle with just continuously accumulates more Prophets for more Hammers, and combine this with Pacifism during peace times... it'll just run out of control... plus the settled Great Prophets also Give out GPP which will significantly shorten the time of the next Great People Produced.
Later in the game when Angkor Wat become Obsolete with Computers, you can change all your farmed tiles into Watermills and Workshops, when running State Property and any excess food goes to Priest, Note that Great Prophet's don't benefit from Angkor Wat so they still Produce 2 Hammers. With the Power of a production City under State Property Civic combined with the Settled Great Prophet Accumulated in the past... That City you've Chosen is still a production Monster.
I haven't done a HE/NE & HE/IW Comparison to find out with is the stronger Production Monster, From a Theory Perspective, it's too hard to determine, because you can build NE Earlier so therefore you can benefit from More Great Prophets earlier which means more hammers earlier, while you can't build Ironworks until Steel, and the difference in time between Steel and Literature is a BIG Gap.