Apple's best bet here would be to co-fund TSMC building fabs just dedicated to Apple, which they would operate as a joint venture or whatever arrangement makes the most sense. It wouldn't make any sense to go it alone on new fabs when they have the tremendous expertise of TSMC to utilize. It might also be reasonable to distribute the fabs as much as possible to different locations around the world, rather than concentrating them near China / in Taiwan (put them in the US, in Europe, in Asia).

It sometimes certainly works strategically to deprive other companies of chips by buying up TSMC's supply, however that can also obviously work against Apple in a big way. If you really believe in your products and the demand for them, you'd want the dedicated supply from fabs you co-own.