I'm assuming by the 16383 limit, you mean the maximum integer size of a variable that a 16 bit software can handle (and its been so long since I did this that I had to look it up). There's no real way to do this without changing the variable type - in this case short integers to long integers.
Lets assume we have a magical software that lets us run a 16 bit software with all the attributes of a 32 or 64 bit system - you'd be able to access more memory, but this is still a 16 bit, short integer variable. You could also speed things up by running multiple instances. One doesn't simply turn a short integer into a long integer by changing the architecture however.
There is absolutely no way, without hacking at the source code (well nearly) to fix this. I guess, if you were a 1337 dissassembling ninja, you might be able to run a dissembler, work out where this variable is and convert it to a long integer. However, at this point you're better off working out what the logic of the software is, and rewriting it.
Sources: C++ header documentation