1) While it’s constitutional, I can’t think of a strong rationale for it other than, “It would be nice to give the Republicans a guarantee of additional electoral votes.”
2) I don’t think there’s much risk that Democrats will copy this tactic for their own advantage. The only states where it’s doable and offers a partisan advantage are ones where one party regularly wins the state’s electoral votes but another one controls both houses of the legislature and the governorship. Pennsylvania and Wisconsin fit that bill for the Republicans; offhand can’t think of anywhere the Democrats have a similar opportunity.
3) The plan would be bad news for Pennsylvania Republican congressmen in swing districts, since the party wouldn’t be running as many pro-Republican ads in the state in presidential-election years.
4) It’s bad news as well for media companies and political consultants in the state. I wonder if any of these groups will lobby against the plan?
5) I wonder what effect adoption of the plan would have on redistricting. The parties face competing interests: increasing the number of seats they’re guaranteed to win and increasing the number of seats where they have a shot. Would this plan change the balance between those interests?