BlackRock’s acquisition of customized index provider Aperio Group, announced Monday, is set to broaden the offerings of the world’s asset manager for financial advisors. It also could help popularize an investment strategy for separately managed accounts — known as direct indexing —  and shake up competition in this area, several industry experts say. For BlackRock, the $1.05 billion acquisition is “just another bolt-on deal that adds to its capabilities, but it’s not a big mover on its own at the forefront,” said Greggory Warren, senior equity analyst at Morningstar.