That's a great suggestion. There is a small weakness in the tool for any diver that carries redundant air, whether it's a pony, sidemount or doubles, and you have identified it: the weight of reserve air at the end of the dive. The User's Manual in the new spreadsheet, and the marginal comments in the current tool point this out, but it could be useful to quantify it.
Some might note that you can ditch a spare bottle's extra weight, but who wants to get rid of gas in an emergency?
The new toy is such an improvement over the old one that I don't want to delay its release any longer. But like metric was, let me put that in the works for the next edition. I like it!
In the meantime, there's a workaround in the appropriate weight ditching tab. In "wetsuit" for example, there are buoyancy figures available at half tank. That might be akin to a diver with redundant air at the end of the dive. By entering zero in the "weight ditched" row, the tool will immediately display half tank buoyancy at depth, any intermediate stop and at the surface. That's the best I can do for now. Of course, you can always use the toy as-is, and then add extra weight at the rate of 0.08 lb/cu ft retained air above 500 psi to get your buoyancy, but that's the sort of thing a numbers geek like me would do.
You're right - we need this capability automated.
Thanks!