I can think of some incentives that would prevent hyperconsolidation. Sliding scale taxation based on some formula including a ratio of revenue to people employed. Maybe take away big company's litigation advantage by making them pay an amount somewhat proportional to their size into a pool that covers the total costs of litigation. Let them recover money on wins. I think such incentives/disincentives would be met with the usual: "but if we're hostile to big business and restrict growth, they'll leave the US for greener pastures!". Is that really so bad? Let companies that are hostile to the US public leave the US. Penalize their advantage away in tariffs or something for fleeing to weaker regulatory environments.

ISPs can't leave and yet we don't seriously regulate them into doing public good or having a competitive market, which is mysteriously somehow contentious politically. Many others can't leave because their talent pools aren't willing to go with them, and that would be even more true if the workers had a government that worked for us.

There is a problem with government being full of people who would rather stay on the receiving end of a money hose than pinch it off for anyone's benefit. All the other apparent problems seem to me to be excuses to protect that. Check greed or we all suffer. You can check greed without stifling ambition. It's a valid choice.