Dear Brett,
I have checked all links you provided in the brief and can say that if they have a good documentation and if they are well-prepared, we can definitely use the 3D Tower Defense Kit logic and change surroundings with the ones you attached. But you should understand that if the game is going to be developed for mobile devices, it will not be compatible with older devices as all those effects use quite a lot of RAM, moreover, as I understand, they need to be dynamic.
And the best for us will be having a well-written spec where all aspects of the game (even if it is based on Kit) are included, starting from splash screen and covering all moments in a gameplay. We are ready to cut the project to milestones and get paid after delivering every part.
The exact price will be given after we see a well-written spec including changes to the standard Kit that will be provided so we can estimate our workload.
Hope to hearing from you soon.
Yours faithfully,
Nizar K.