Quote: "Seems like it's going to take some time for this tool to be done."
Not that long really. The work I've done so far took just over a week.
Quote: "I think I will make a small utility myself to just facilitate the job for my next project (right now I am hardcoding rotation data manually), and then use Spriter in the long run..."
That's up to you. I have a few handy functions if you decide to go along the parent / child rotation route (the way I've done it). The main one is my "rotateSpriteAbout" routine which rotates a sprite around a point by a given angle. I plan on putting it the UCF project but I can post it here if anyone wants it... here it is (it works in virtual resolution mode only in this format):
function rotateSpriteAbout(spr,x#,y#,a#)
setSpriteAngle(spr,getSpriteAngle(spr)+a#)
sx# = getSpriteXbyOffset(spr)
sy# = getSpriteYbyOffset(spr)
dx# = sx# - x#
dy# = sy# - y#
a# = atanfull(dx#,dy#)+a#
d# = sqrt(dx#*dx#+dy#*dy#)
x1# = x# + d#*sin(a#)
y1# = y# - d#*cos(a#)
setSpritePositionByOffset(spr,x1#,y1#)
endfunction