I think it'd be too sweet, but might be a good starting point. I'm think I'm still leaning more towards slightly sweetened milk biscuits, cut somewhat thick and in squares rather than circles. I have a recipe I came up with from figuring proportions on a package of biscuits we liked and then experimenting with - that might actually be close! I haven't made those in forever...we even made a pattern pricker for them!
Lembas are supposed to be mildly sweet, so I think you are on to something there.
If Tolkien were a woman, he would of written a recipe for lembas in the Appendix! LOL!