I think OP_RETURN policies that are more accommodating will have 2 dominant outcomes:
#1) those who can think of a use case for large amounts of arbitrary data - but discouraged from doing so by having to go through the trouble of figuring out how to abuse the UTXO set - will suddenly have a convenient mechanism for implementing their use case; and,
#2) those same people - due to the ease of achieving results vis a vis #1 - will be inspired to come up with more such use cases.