It's really unfortunate how animal agriculture takes over terms like "protein" and now "regenerative farming". We have more choices than the two you have laid out. It's not only a choice between farm animals or destructive intensive monocropping (which we already do to feed animals now btw).

First look at the macro. The majority (more than 50%) of cropland is used for feeding animals so by taking them out of the equation we have freed up a ton of land and possibilities. Once we no longer have such a high requirement on crops grown we can look at changing how we grow them.

Now ignore what cows are to you for a second and just think about what they do for the soil. They are eating whatever is growing there processing it, using a huge amount of those nutrients to grow, and depositing the rest on the ground as fertilizer. It's an open loop system where the majority of nutrients go to the cow then the cow is carried off the farm to be killed and eaten and those nutrients never return to the land that grew the cow.

Instead we can look at composting, crop rotation, letting land go fallow and other farming practices to keep the nutrients on site. These include no till farming where we minimize the soil disturbance and keep it healthier and intercropping where multiple crops are grown at once in a way that support each other and balance the nutrient requirement in the soil.

Finally in a alternate universe, that I want to stress does not actually exist, where we have to have cows and sheep in the field to maximize the productivity of that field during fallow years then we could treat those animals like service dogs now. We let them live out their lives doing what they do for the soil, but we do not have to kill them every year and breed new cows and sheep to take their place. Cows live for 20-25 years. We would need a tiny number of animals to accomplish that task. If we kept to the bare minimum number of animals for keeping the soil healthy we would effectively have a vegan population because there would be so few of them.