Seems like the next logical step. Problem is, the UK fanbase get all TNA's PPVs for free. Would seem a strange business tactic to promote a UK PPV to a US audience and have the UK audience get it for free.
Stay up for it? If TNA was to run a show at 7pm UK time, that would mean it would be live in the US in the afternoon when everyone is eating their dinner. I don't think there is much market for a TNA PPV at 12 o'clock on a Sunday afternoon.Or like the OP said, people would just stay up for it.
How can WWE have exclusive rights over a PPV service? TNA is part of the Sky family too, if Sky had an objection with TNA they wouldn't have had them on Challenge TV in the first place.TNA can't run PPVs over here. TNA is signed to BSkyB, who broadcast them through Challenge TV, which is a free to view channel. Sky would only allow TNA to run a PPV via Sky Box Office. WWE has exclusive rights to Sky Box Office, so TNA wouldn't be able to do a PPV.
Also one of the best features of TNA is that its on freeview, so most of the country can view it. If they had to pay money to see it, there is a risk of over saturating the market, so WWE have done. I remember they uproar when we had to pay for Royal Rumble 2002.