Designs using the 555 are easily converted to using a 556 and visa versa. The chips are electronically identical, except the 556 is two 555's with common power pins. I used the term "555" generically to mean either chip.
To suggest that a 556 based design would be more versatile doesn't make much sense. At best, the space saving is quite small, and if you use the SMD versions, it is even less. What do you need to do with a 556 that two 555's can't do?
I agree with atferrari about using a micro, if you really want versatility, such as changing from full steps to half steps, etc.
John