Build a 2.5d war game.

I want to build a war game in 2.5d. all assets to be provided by developer based on my ideas. The complexity and size of game would be similar to Puzzle and Survival game which is based on puzzle as well as building armies, upgrading equipment with lots of in app purchases. Attacking other's bases. Etc.
Estimated time it would require to develop game could be upto 6 months