TL;DR
Add optional separate grid size when BP is positioned absolutely.What ?
Imagine blueprint, that has 96x96 grid size and is absoultely positioned to fit 3x3 chunksas a result top left corner of this BP can be placed only in top left corner of chunks [0,0], [0,3], [0,6], ..., [3,0], [3,3], ...
with separate grid size for abs. ref. point set to 32x32 top left corner of BP would be allowed to place in top left corner of any chunk