1 - JJ I gather that it is possible to add text into nodictionaries, and/or the website owner says he will do that upon request, if that proves helpful.
2 - I suspect you are right that google docs is a good option. Would a spreadsheet perhaps work better, or does Brill suggest a format? I would not think "CSV" would be good enough but something like that which is text-based might work.
3 - You've probably seen my recent comments on GITHUB in regard to working with it on the "Epicurus College" materials. I am pretty much getting to the point where it's not quite as intimidating as it used to be to me, but it has great advantages if the material you're working on can be "text-based" instead of binary like Google docs or spreadsheets would be.
The tremendous benefit I see is that it allows VERY fine-grained collaboration, which is apparently what "merging" and "pulling" and similar terms are all about. The benefit is that the master-overseer (you) can get help from others with the others submitting "pull requests" (I think that's the term) with the material that they have typed and/or corrected. You as project leader get to see a "differential" view of each line in text format, so you see EXACTLY what is being proposed for addition or corrected, and then you "merge" the corrections/additions that meet your approval. It might be that such fine-grained supervision might not be necessary, but that's a factor that has stopped me in several efforts at collaboration in the past. It's pretty disconcerting to think that multiple people are editing the document without the main coordinator knowing what they are doing and approving their contributions. Github and similar "git" services were designed to meet those challenges and it seems to work pretty well. Here's a screenshot showing how the review system works, highlighting the original vs changed lines:
It may seem like overkill, and it might be, but the more I get familiar with it the more I see how it's a really good fine-grained collaboration tool for multiple contributors.
Hard to say if it would be worth your time but wanted you to be aware of it.
PERHAPS one approach would be to start with getting all six books into no-dictionaries, generating some kind of rough draft, and then creating markdown (text) files for each book, posting them to github, and then editing them in collaborative fashion as you have time.
Not sure, but I would dearly love to have an interlinear Lucretius. Like you, I've looked and I haven't found one, and don't believe one exists.
Similarly I was looking for an interlinear of the DL bio of Epicurus, or Cicero's "On Ends" and haven't found any of it.
Here is a discussion of how a text-based table looks using the markdown format that would work in a git collaboration system: