Everything listed here has been thought through, deemed possible to do, and practical. This is what I'd like to end up having (while keeping things realistic):
The ability to load programs as a string or from a .8xp file will be pretty important, I think. Multi-program support is plausible, too. This means subroutines! Most everything reachable in BASIC will be there. I want to exclude things like Send( and GetCalc(. Even though networked gaming sounds cool, it's not first priority; maybe later, after everything else works. There will be a program editor in the applet (not like the one used on a calc). You'll have the option of running things at the speed of any 83/84 calc.
Time functions won't be added immediately. They ain't extremely important to me. There will be keyboard support for every key on the calc, all re-configurable.
I know people are doubting a bit about speed (too fast or too slow, unrealistic). None of that should be a problem, though. Delay will probably be adjustable. There will also be a little count-down, one special to each BASIC command, to give it realistic timing. Also, before a program is run, it'll be kind of mini-compiled, in a way. This will put the program in a format easily (and quickly) readable by the whatever.
Only program-running will be supported; no normal calc activity. As mentioned not too long ago, there will be support for things like Omnicalc and Xlib. It shouldn't be that hard, really. I'm considering pixels fading on and off instead of just changing abruptly, just for grayscale's sake. That's not for certain, though.
Saving things will be a must. Otherwise, what's the point besides just testing things? It should be able to save things in a human-readable format, as well as .8xp.
I don't know whether I'll release the source code or not when it's all done. Probably. Unless someone dies or something, this sdk will be released as both an applet and an executable jar file.
I don't think I left anything out. If I did, I'd like to know, just to make sure I didn't make it that way, forgetting something. Remember how badly I want suggestions (very).
How does it sound? All that remains now is doing it...