The ECB, in my opinion, would be wise to come to some sort of formal agreement with the PCB.
If England is to be Pakistan's "home" for playing international cricket for the forseeable future, then in my opinion it would be beneficial for both boards to try to come to an agreement with regards to allowing centrally contracted Pakistan players to play in the County Championship without restrictions.
The big danger for Pakistan is that they become uncompetitive due to English conditions being alien to them. A good, competitive Pakistan in Tests and ODIs will not only help keep the cricket flame burning in Pakistan, but also has the potential to be extremely lucrative to the ECB. There's a large Pakistani expat community, particularly in Leeds and Manchester, and the prospect of seeing a strong, competitive Pakistan take on the likes of India, Australia and South Africa in England would be a mouth watering prospect, both for the Pakistani descended community in England, but also for the "indigenous" English cricket lover as well. Grounds would be sold out, which benefits the counties staging Pakistan's "home" internationals financially, and Pakistan would be stronger for it.
Incidentally, I'm hoping that Cricket Scotland gets in on the act as well, there's a huge Pakistani community in Glasgow, and I'd love to see Titwood becoming one of Pakistan's "home" venues for ODIs played in Britain.