His whole plan had been destroyed.
Everyone rejected his offer, leaving him with almost 15,000 SoulStar Fragments to use. Michael wanted to strengthen his friends and he had no clear way to use the remaining SoulStar Fragments right now.
It was possible to upgrade one of his Soultraits a little, but none of them could receive a complete upgrade. They wouldn't advance to the next star rating.
'What about fusing more Soultrait Symbols? Blood Manipulation should suit Superior Constitution quite well.'
Using Insert with a bunch of Soultraits to provide his other Soultraits with unique perks would strengthen them tremendously. Furthermore, given his experiments, inserting low-ranked Soultraits into Soultraits of a higher star rating would increase the upgrade cost only a little. The Essence of the Soultrait wouldn't be changed, after all.
"But wouldn't it be a waste to fuse Blood Manipulation as a sub-Soultrait?"