Fair enough. But I still think my suggestion is realistically feasible... Find whatever place in the source the paths to the history files are kept in the "original" source (where it writes history upon every enter), and edit those paths to place "/tmp" in front of them. And then add the code from the Nokia patch that makes them write the history out at exit (but don't override the former like the patch would), and change that code to pull data from the "/tmp/[whatever]" and put that into the standard [whatever] ash history upon every shell close. That way history accumulates from all the concurrent shells in the order the commands happen across the board, and is saved on every shell close (with the above patch/workaround by you guys, even when you hit the above X.)

Busybox is coded in C, right? iDont, where do you keep the latest source for this package (my apologies if you mentioned it in this thread already. If you have just say so and I'll go look)? If I get the time I'll take a look at the source see if I can improvise a shitty patch to do the above. (I probably can't, but I can always get my own hopes up before realizing I can't do it.)

- Edit -
NVM - it's right there in the second post.