(You can check this with chains like Cleveland-Detroit-Chicago-St Louis-Kansas City; each interval is less than 300 miles)
I don't disagree that it would need to be an incremental process.
I've seen a few of these proposals now. The good ones have a clear rationale for relocation: the Australian Federal Treasury, for instance, is moving a sizeable chunk of their workforce from the capital (Canberra, population ~400,000) to Sydney (population ~5m). Why? Because the financial industry in Australia, and many regulators in the Treasury portfolio, are based in Sydney. Seems logical to do this if you agree that lower-level, person-person connections are valuable (I think they are).
The bad ones have no clear rationale, and co-incidentally the relocation target happens to be a marginal electorate in some regional area...
I think it's fair to say that it's not been a massive success, and that federal employees generally did/do everything they could to stay in the old capital.
Aside from the fact that the entertainment and cultural options available tend to be limited, distance from the rest of the family and friends, as well as the perspective of being tied very strongly to a single employer are usually unappealing.
You run a real risk of losing anyone senior/competent, and keeping only the most junior of your staff, who have no other option but to relocate.
To stand any chance of success, I would think that the process needs to be fairly gradual, with good transport connections with the historical centres of activity.