Shamsi has spent most of its life in the hands of Emaratis (that is LOW by any standards) and americans. The base can go back in the hands of arabs/americans... at any second.
Plus, Americans and arabs basically roam free in Pakistan. So do the taliban and a ton of wahabi terrorist animals. Trust me, if one border needs securing, it's the Iran-Pak/AFG border, not the other ones. We have clearly defined enemies along our other borders. In the West, it's the Americans. In the Persian Gulf, it's the US aircraft carriers and bases in oil islands. In Pakistan though, the problem is that you never know wtf is going on. arabs roam free, Americans come and go, wahabi thugs are walking like it's the "Wild West," the ISI itself LOVEEEES to fund the taliban and take money from arabs, the country's leaders have time and again sold pakistan to khaleejis (emaratis, saudis etc...). The unpredictability is a problem.
As I said before, when a country leases an airbase within its territory TO UAE, you need build a fence around it and do it quick.