I think the main costs for wide person-affecting views relative to narrow ones for someone who wanted to solve the nonidentity problem are in terms of justifiability (not seeming too ad hoc or arbitrary) and complexity in order to “match” merely possible people with different identities across possible worlds, as in the nondidentity problem. I think for someone set on solving both the nonidentity problem and holding person-affecting views, there will be views that will do intuitively better to them than the closest narrow person-affecting in basically all cases. What I’m imagining is that for most narrow views, there’s a wide modification of the view based on identifying counterparts across worlds that would just match their intuitions about cases better in some cases and never worse. I’m of course not 100% certain, but I expect this to usually approximately be the case.
I think the main costs for wide person-affecting views relative to narrow ones for someone who wanted to solve the nonidentity problem are in terms of justifiability (not seeming too ad hoc or arbitrary) and complexity in order to “match” merely possible people with different identities across possible worlds, as in the nondidentity problem. I think for someone set on solving both the nonidentity problem and holding person-affecting views, there will be views that will do intuitively better to them than the closest narrow person-affecting in basically all cases. What I’m imagining is that for most narrow views, there’s a wide modification of the view based on identifying counterparts across worlds that would just match their intuitions about cases better in some cases and never worse. I’m of course not 100% certain, but I expect this to usually approximately be the case.