Yes, if you're making the file in Word itself, I think if you save as a Plain Text file, Word is based on Unicode as far as I understand it. I'd still save the file as .txt and then rename with the .dic extension, just to make sure it saves with the proper formatting, or lack thereof.

I really hope it works. I've been saving words a few at a time when I spell check documents, but like you I'd want a simpler way to jump-start the project rather than having to build it up over time.