It looks like you could edit the bitmaps in order to change the appearance of things, but other than that, the odds seem slim to none.
When I look at the files for Civ II, it really seems like the programmers went out of their way to make different elements of the game moddable, even if they didn't know it would become a trend.
In other words, it was probably the exception to the rule back then.
With OP1, all the variables and data and such are, at the very least, not readable by humans. You might be able to reverse-engineer some of the data like the community did with OP2, but OP2 took years of effort to crack (not so much crack as very slowly wedge open actually). Several people are of the opinion that it would have taken less effort to just build our own version of the game from scratch.
I think that may also be the case with OP1, especially since it is an incomplete game in the first place, by the time you put in enough effort to mod it to any significant extent, you might as well have just rewritten it entirely, and started modding from the source code.
