1. Learn ABAP. For SD, a module with a lot of userexits, enhancements and VOFM is would be an advantage. It will give you the possibility to become a Business Analyst for an end user company. This last option have the advantage that you can have a serious exposure to other modules (if the end user company is a midsized company, it's hard but it's a guarantee of learning). So, if you come back to a consultancy company, your capabilities for integration will improve and your empathy with customer needs will be a natural instinct. Other advantage, it's a natural way to become a techno-functional.
2. Other modules. I don't know CRM, but Industry Solutions are an option, for instance, IS-Retail. Other options: CS, MM. But the blog by Thomas is better than this second suggestion.
I hope this helps you