In case that it may be useful, posting some of my prev experience here.
*snipped*
I found the post helpful and insightful.
I hate BMPs. I too walked the road you have described, and at the end of that road I stopped playing DF for about a year.
I started a PNG tileset several weeks before the release of DF v0.31, and had no plan to release that tileset, let alone a BMP version of my tileset.
I did not except the release on the 1st of April. I started looking for BMP tileset to play DF v0.31 with, and found a void to fill. I then took upon myself to provide a temporary BMP tileset to myself and others until the d# merge occurs. I was expecting a merge withing days, two weeks at most (heh!)
I simply do not take any long term decision for my tileset with BMP limitations in consideration, because I am longing for the day that I will be able to pour magma on that BMP version of my tileset.
I make improvement to the PNG tileset, create an approximate reproduction of those improvements in the BMP version, and make BMP hacks when needs be.
And that is why I'm following that road to 'nowhere' with the BMP tileset; I'm using the BMP as a testing ground to get feedback for the PNG version. (I actually never expected the bmp version to get more than 10-20 downloads.

)
As for the RAW issue, I've already made a firm decision: I will not make a tileset that does not require raw changes.
Reasons:
There's already many tileset that require no raw changes, and there's very little I could improve on those tilesets without changing the raws.
There would be very little in common between the 'clean' and 'dirty' versions of the tileset, so it would be like doing two separate tilesets at the same time.
But, I can (and do) provide the unit graphics package as an independent download, as those do not change the default raws and they can be used with any other tileset.
Anyone can download a clean tileset and the unit package if they want.