After getting frustrated with the Tuner a while back, I started on a CLI to make a simple file format to make layout editing easier. It's still very rough, but grit on putty was also pretty rough when people found it, so rather than letting it sit until I get around to improving it (which could be months or years...), here it is as it stands.
At this point, it's basically equivalent to Dido, but with a slightly more user-friendly file format, and open-source (and it's been updated in the last year, though I make no guarantees that twidlk won't look just as dead as Dido a year from now ). It is written in Haskell, so I'm not expecting massive community contributions, but it should at least be straightforward to run cross-platform.
I have a bunch of plans listed on the README for things I'd like to do with it; I'm also open to suggestions (I already noticed a couple looking at the dido announcement thread).
And feel free to ask for binaries/packages for various platforms; that's a low priority for me, but I do have access to Linux, OSX, and Windows, and can probably put together builds for any of them if I know people will use them.