I believe that Turkmenistan pipeline should be scrapped for now. IPI pipleline is the way the to go for Pakistan to meet its needs, and it also wouldn't have to spend that much money which it is trying to spend on Turkmenistan since the project will be funded by both India and Pakistan. Once IPI is built and is meeting the requirements of Pakistan and India, and Gawadar becomes a successful port (which inshallah it will be) i do think that Pakistan can pitch in a deal with the Turkmenistan to offer its oil to Gawadar port, that way Pakistan can earn more than what it will spend. Let them spend their money to construct their own pipeline. What do the members think about this scenerio?
I'm not completely sure, but TAP is being funded by the American oil companies (it's an American project, why is Pakistan paying anything for it anyway). After all they've always wanted TAP to come about from a long while back. They can't use Iran in order to ship the barrels, the nearest country would be Pakistan , unless they can make something of a line up and around Iran, through Iraq and winding around Saudi Arabia which would be too expensive and probably too big to do. If that pipeline is free for Pakistan, and if the IPI pipeline is paid for by Pakistan, Iran, India, then it's possible to have both. This could be used by Pakistan to force either the Iranians or Turkmens into lowering the price of gas to them by favouring the cheaper line.
I would have thought the TAP line would be more favourable to Pakistan, since the Americans want this for Gwadar. The Iranians are only after money for themselves, though the Americans and Turkmens are too, both of them know Pakistan is their only warm water outlet, and so they'll probably give Pakistan gas (and oil) at a discounted price. The attitude of the Iranians is puzzling like AgnosticMuslim said above, since there is an alternative which probably would be cheaper for Pakistan perhaps. Who do you choose? The Americans/Turkmens or the Iranians? Iranians might be more trustworthy for Pakistan, but the Americans/Turkmens would be offering a good deal since they need Pakistani help, the Iranians don't. I agree with your sentiment below, that it would help improve relations between neighbouring countries though. If the Iranians lower their price to compete with TAP prices, Pakistan should favour the IPI, if not, take your pick. If the Americans are in charge of the TAP, having a second pipeline of the IPI would mean that even if America wants to stop export to Pakistan (which it wouldn't since it needs Gwadar), there's IPI to take over energy supplies.
I think I've come to my final opinion. Build both pipelines.