...I just hit F5 with the wrong window selected and lost a long post.
TL;DR VERSION!
1. I think that first paragraph is the greatest compliment I have ever received. Thank you.
2. I mostly like your proposed format. I'm not sure about the sanitization, since IMMUTABLE tokens don't include special characters, and only IMMUTABLE tokens should be literals in raw format definitions. Unless you're talking about including this kind of code in actual raws as part of your injection functionality, in which case that kind of handling is well outside of BAMM's scope for 2015.
3. I'm also not sure about the KILL_RULE and ADD_RULE functionality. That seems like a problematically oversimplified approach for multi-mod merging. I'm still formulating the exact approach I'm going to take for mod merging, but I want it to be subtler than this. I don't want to use a sword where a scalpel is called for, and hardcoding what tags to add or drop into the tag templates themselves? That's a claymore.
4. What value do you hope standardizing the formats between the two tools will add? The only real benefit I can see is that when new versions come out both apps can be brought up to date by one person. Which isn't nothing, but given that the two tools have different goals, I'm not sure that it's enough. Obviously I really appreciate the input, and I'd like to continue bouncing format ideas off each other even if standardization doesn't happen because your ideas are pretty rad; but unless there's some greater value to it that I'm overlooking, I don't think standardization for standardization's sake is enough of an incentive to justify the additional work of handling features that only the other of us needs.