Now that I think about it, it would be better just to include AC3 for the mkv release and let people put in uncompressed audio on their own, if they want to. Doing so is very easy, as you said, and it would reduce the file size of the upload considerably. Save lossless for the version in Bluray format.
I just realized that I didn't actually know how uncompressed audio is handled in Bluray. Looking it up, I find that it wants raw PCM, with the big-endian byte order. (The channel mapping is also different than other formats, though this only matters for surround sound, not stereo or mono.) This differs from WAV, which is little-endian, so at the smallest computing level, the information is being stored in reverse: most significant bit first, instead of least significant.
What this means is that the inclusion of PCM on a Bluray probably depends on what the authoring software will accept for input; whether the source file can be used directly or whether it has to be byte-swapped and converted to raw audio data. Something to keep in mind when the time comes.
At any rate, I'll upload all the original mixes (AC3 first, lossless later), once I've had a chance to look at the mono mix and see exactly how much level reduction is needed to match it to the other tracks. I think you've already got the 1993 version at 320 kbps that I sent you for the previous release, if I remember correctly, so that's taken care of already, and I guess something like 256 for the stereo and 128 for the mono seems reasonable. The 5.1 could be encoded at 640 kbps to maximize the quality, since it doesn't have to be restricted to 448 as it does on DVD. (In this case the DVD release would need a separate encode, but that's no problem.)
Editing to add: It occurs to me that the best way to include lossless audio might actually be to use DTS-HD MA for all of them. This is usually used for 5.1, but other channel configurations are supported as well. It would have a lower file size compared to PCM, as well as having a regular DTS encode built in to it for people without HDMI receivers. Even including both that and the AC3 version (to make sure that even people without DTS decoders can still hear the sound) would still take up less space than PCM by itself.
As I recall from watching Puggo Grande, the 16mm capture of the mono mix is really rough and scratchy sounding. Belbucus did quite extensive cleanup work on his restoration, including careful noise reduction on the rougher parts, so even though it's not up to par with what could be done from a higher quality recording, I don't think there's a better source for the mono version available to us. Plus it's already perfectly GOUT-synched . . .