2) Sign one of the best position players available
Losing Ohtani not only affects the Angels future rotation, but it affects their present and future lineup. The Angels offense was average at best with Shohei on the team, and will certainly be below-average if they don't make an addition after losing him.
The Angels simply cannot replace Ohtani. He won the MVP for a reason, and the NL MVP won't be available. While he can't be replaced, the Angels can do their best to try and add a big bat to this lineup.
Cody Bellinger is now the most-expensive position player free agent. A Bellinger signing would come with some risk considering his volatility offensively, but when he's on, he's an MVP-caliber player. Bellinger won the NL MVP in 2019 with the Dodgers, and was a top-10 finisher this past season. He'd certainly provide a boost.
If they decide Bellinger is too risky, the Angels can sign one of the many DH's available. J.D. Martinez is arguably the second-best hitter available, and will certainly be leaving the Dodgers after Ohtani signed there. Jorge Soler just had a monster year for the Marlins and can provide most of Ohtani's power.
Whoever it is, the Angels must try to bring in a game-changer. It won't be as good as Ohtani, but it'll be something.