[usrusr]

No amount of "ASIC unfriendlyness" will bring back the cute old days of distributed desktop mining. Concentration to a few specialists is the natural end game of any PoW scheme, no matter how much effort you put into inconveniencing them. If a highly concentrated cryptocoin network is not good enough, cryptocoin is not good enough.

(your last point however is valid nonetheless, the scenario of large blocks of capacity jumping between networks and how deliberate algorithm design tweaks might offer some protection)