Well, it depends whether you want to buy something off-the-shelf or build something yourself.
If you could be a little more specific as to how many stepper drivers, how many servo controls, and what kind of User interface you need, then we'll be able to help you.
This message was posted on behalf of Intel Corporation
Thank you for your patience. We’ve been reviewing your case and the best alternative is using an I/O expander. Most of these expanders are based on I2C, which will allow you to use up to 16 GPIOs. One of the most popular expanders that I’ve seen is the MCP23017. Even though, there’s not a complete example of how to use this chip, the shield testing report has some guidance on how to run an example that uses an MCP23017 library.
The Shield Testing Report can be found here: http://www.intel.com/content/www/us/en/support/boards-and-kits/000020775.html
I hope you find this information useful. Let us know your results.