Game looks very imbalanced at the moment for different reasons, however many of things would be avoided by having at least one more species(kind) to play with. But this is topic for another thread, just wanted to bring that out.
My suggestion for the towers purpose improvement consists of following:
Every race should have their own towers they can build, why?
- Warlords can move with increased speed of +1 to +5 in between ark and tower or between towers which race they belong to; or based on number of towers that are built in your realm of certain race, your bonus movement will increase to a # number (limit because of the late game or island)
- When defending in their own race towers get 5% - 10% def bonus (or same rule as second part of example 1)
- Resource and troop supplies will give 5% - 10% bonus to the race whose tower is holding them (or same rule as second part of example 1)
- When defending, army of race that tower belongs to gets + # morale or + # initiative (or same rule as second part of example 1)
- Cost of upgrading the supplies held by a tower are cheaper for the race that tower belongs to buy 5% - 25% (or same rule as second part of example 1) - or/and more expensive for the other race/s
- Same as point 5, but only towers themselves
- Number of troop supplies held by a race speeds up troop production of particular troop type (cavalry/infantry/artillery) by 10-25% of that race
- Map will bring better experience and be more involving
Please bear in mind that bonus values are just examples. Idea can be improved of course...