Eminent domain is a dirty, dirty hack. "We can't figure out how to make property work, sod it, lets turn off property and just take it at gunpoint".

There is a much cleaner solution that works without breaking property: buying options. You want to build a road, but you don't want to he held hostage. So you play a game rather like connect-4 by buying (for trivial sums) contractual obligations to sell to you at a fixed price within some sensible time limit. Once you have any workable unbroken line of optioned land between A and B, you exercise the options and buy it. All a hold-out does is cut himself out of the deal, since you can route around him.