I would like to suggest a rework to the wonders.
First of all there are many problems with wonders i would not discuss today, especially regarding the usefulness of some (Hephaestus) and uselessness of others (Ares). Nor will i discuss the "faith-nuking" with multi accounts. Both of those topics are valid and important so they require separate discussions.
1. Problem i see with miracles is that you can only upgrade them to level 5, and that they are only way to donate luxury resources in game currently. their upgrade cost is relatively small - which is good, since this means that even new players can quickly get them working at max level.
2. I would add 10 extra levels, each costing more than the others:
Lv.6 - 500.000
Lv.7 - 1.000.000
Lv.8 - 2.000.000
Lv.9 - 4.000.000
Lv.10 - 8.000.000
Lv.11 - 16.000.000
Lv.12 - 32.000.000
lv.13 - 64.000.000
Lv.14 - 128.000.000
Lv.15 - 256.000.000
3. So what would those extra levels do? They would provide various small, but constant bonuses. They could apply: A - based on your own faith level in your town. B - based on faith level on island. C - constant boost for the entire island.
4. Now about the bonuses of various gods:
Hephaestus: up to +10% counter-espionage (1%per level)
Hades: Corruption reduction up to -5% (0,5% per level)
Demeter: extra happiness up to 200 (10 per level)
Athena: research points production boost up to 10% (1% per level)
Hermes: port loading speed boost up to 10% (1% per level)
Ares: troop training speed up to 10% (1% per level)
Poseidon: Transport ship speed boost up to 10% (1% per level)
Colossus: gold production boost up to 10% (1% per level)
5. Of course the cost of upgrades and various bonuses are merely suggestions, and not set in stone. i just wanted to start a discussion regarding this topic.
Feel free do add your ideas how to improve the miracles, so maybe some changes will happen in the future.