Hi fellow,
So as i understand, you want to create/setup a new Map service that can interpret/use/integrate information fron GMaps, CartorType and Cartcss, aren't you? If that so, the range to deliver this products is 1-4weeks like the offer says or each requirement could be estimate independently that range?
In any case, i can offer you two methods to work this project, as a individual i sure can help you and make this through using a middle interpreter to create the 'uniform' map style, which i would like to propose it use JSON below, 'cause its simplicity, robustness and Python compatibility.
Then when the 'uniform' map is ready we have to create a parser/writer for every format you like, so we can make just interpreters/writers uniform Map <-> Any map, in that way we can use this as a bridge for any conversion.
The other method is with the same logic but using a SCRUM Team, it means, an entire highly qualified dev-team at a real good cost, this could accelerate your project at a very low rates, but with real high quality of the product, using TDD (Test Development Driven) and SCRUM methodology.
We can discuss any of this proposal to give you a RoadMap when the requirements are clear... if you chopose the SCRUM team, we can star develop the basics req's while we defined the complex one, so we can work on parallel and progress much faster.
Looking forward working with you,
Rafael Aguilar
Solutions Architect