Daishaclaire: If you're right, dtgreen, and the experience point total is the sole determinant of whether a character's stats are modifiable in-game, then it should be easily done with a memory editor.
I'm not a windows user, but I've used the linux utility scanmem on the dosbox process for some of these old goldbox games, and experience is the absolute easiest value to pin down. (Ability scores though, since they very rarely change in gameplay, are pretty difficult to pin down.) You just scan memory for a particular character's current experience point total, fight one battle, and then see which of the previously matched values now matches the character's new experience point total, and usually that'll be enough to narrow it down to a unique memory address, which you can overwrite with the starting total and edit your character's abilities from within the game.
Probably only Linux or Mac users will be interested in this method since Gold Box Companion is a windows utility, so on linux you do
enter in terminal:
sudo scanmem <DOSBox process ID>
<character's current experience total>
[go win a battle]
<character's new current experience total>
[repeat until a single value in memory matches]
set <character type's initial experience value>
then you can use the reset command and start over searching for another memory value, if you'd like.
Unfortunately I can't recommend a Windows memory editor since I'd be relying on just a few minutes of googling and I don't want to accidentally recommend a malicious or poor quality utility. Still, the procedure should be similar, maybe even simpler if you prefer GUIs.
Keep in mind that you can seriously screw up your game or even your whole system mucking about with a memory editor, so be careful and don't go overwriting values until you're sure you've matched the proper address. (Especially don't overwrite multiple addresses at once, do enough searches to narrow it down to a unique value!)
Thanks for mentioning scanmem. I never heard of that utility, so I have to try it.
On Windows, you can do this sort of thing with Cheat Engine.
