Even using the terms SAARC and EU in the same sentence is an insult to the latter. Unlike SAARC, EU has been a successful and meaningful experiment in regional integration.
Even though the whole premise that Pakistan might somehow take cue from Brexit and mount an exit from SAARC is based on loose ground and does not leave a flattering account for your potential as a researcher, even if such an event were to take place by some fluke, it really wouldn't make a difference because SAARC is little more than an excuse for some ministers and bureaucrats to enjoy a paid holiday on tax payer's money unlike the EU which is a fully functional institution that has had tangible impact on the political and economic trajectory of Europe.