I would lay off the small bass. You want a large abundance of bass. Often times, I recommend a 15" minimum length limit for the bass. The reality is that a stockpiled bass population rarely has bass over 15" so putting this limit on is essentially the same as a "catch and release". If a few bass sneek past the length limit then I say go ahead and harvest them. Chances are it's old and won't live much longer anyways. Keep in mind this situation applies to a stockpiled bass population. Oh yeah, the sizes I'm talking about are typical for midwestern ponds. Perhaps the southern states could raise the minimum length limit a couple of inches?? Bottom line is that good bass recruitment and high densities are needed.
The only exception I can think of is if there is an overabundance of prey for the crappie (minnows and shad). If this is the case, you could probably have more room for error when it came to harvesting bass. But a lack of sufficient prey is usually the case, so a reduction in crappie numbers is needed. This is done by making sure the bass eat the heck out of them, and that the angler keeps his/her freezer full.
As far as white crappie go, I have seen them do well in ponds, but this seems to be the exception rather than the rule. Just remember that black crappie do better in clear water (say greater than 18-20" visibility) than whites. Since you need bass, you therefore need the water clear enough for the bass to efficiently prey upon the crappie. Since the water needs to be clear, you're best bet is to go with black crappie.
The cool thing about fish management- particularly pond management- is the experimental side of things. If you have an idea and after you've done your homework, then go for it. The worst thing that can happen is that you start over. This can be expensive depending on the the size of the pond, but it's an option. Otherwise, you can be safe and do what's been known to work. I learn more from ambitious pond owners than I ever have from reading books.
Having said that, I would personally make sure my pond had suitable habitat conditions and then I'd stock black crappie.
