CCBill is and always has been a great company with some great people, likely the biggest reason it's still in business and thriving, but the WMS was a complete failure. We tried it for very little time before reverting.
If I may make a suggestion, why not do this in stages.
Stage 1: Duplicate your existing system, with new code from the ground up (assuming this is necessary). This will allow you to go forward then without doing "patchwork" to an old system coded many years ago.
Stage 2: Add in new features you have planned for WMS slowly, one by one, to allow testing to be much more prompt. Once resolved, move on to the next feature until after a few months, you will have a brand new, solid product.
At the same time, during Stage 1 you should correct the negatives with your existing Webadmin. It is archaic and many people hate it, especially in regards to the slowness and unreliable way it generates reports. It is "clunky" for lack of a better term and hasn't been ushered into the current day and age while the rest of the company has progressed forward in other areas.
For example, your current system works horribly in Chrome. Chrome is a browser gaining ground and everytime I submit something in Webadmin, I need to re-try usually 4-5 times to get the "CCBill Loading" screen to come up.
No offense meant, but it seems for a good many years now you guys have been "fat and happy" to improve that aspect of the product; with reason I suppose, since few is the competition on your level.
All that aside, perhaps the biggest reason is I also just loving giving Paul K. more work to do
