I guess I should start of by saying that ATM, Foobar ain't for me. But I do like several of its features, particularly its built-in functionality for calculating and storing replaygain in album mode.

I'm trying to get good replaygain support in QCD. I know of 2 QCD-compatible plugins for replaygain: the xcopy plugin, which has MP3gain support, and the WinAMP 2.x replaygain DSP plugin. The problem is that AFAIK none of them directly supports album mode replaygain calculation.

One idea I had is to use Foobar for the calculations, and then export that data into something usable by the DSP plugin. (I'm not big on fb as a player, but wouldn't mind using it as a utility) I was thinking Tag (or some derivative) might be able to handle this. It would go something like this: Foobar rg calc -> Apev2 tags for the data -> Tag to extract the data, whip it around a bit into the format used by the rg dsp plug -> out to a txt file -> copy & paste by me into my replaygains.csv file. Setup the rg plug so that it applies rg values that have already been calculated (and stored in replaygains.csv) but doesn't calculate new values, and enjoy! Or so the theory goes... My poor Tag/scripting skills just ain't 1337 enough for the job.

Does anyone think this is possible/plausible? Anyone think they could knock together a small app/script to handle this? Anyone have a better idea? Anyone think I'm completely nuts?

Depends which format you talk about.
MPC and Ogg Vorbis plugins have built-in replaygain support.
If it's these formats you talk about you need to use either foobar to calculate the gain values or their respective replaygain tools which can be found at the formats download section.

For mp3 you can use MP3Gain but you need to disabled the tag writting feature for it to work with other players than foobar ATM. This way it will modify the MP3 files itslef and therefore the player doesn't have to support anything.