What is a 25mm Bullpup? That's only about an inch long! You mean 25 caliber?
Every PCP I have owned has had problems with reliability; I used to think they would be the perfect, all-around weapon, but reliability is the down side. O-rings and other seals go bad, valves don't last forever, and they are expensive. if you are not crazy about accuracy, power, or loading speed get something simple and cheap that is easy to work on; Bullpups add complexity, especially forward cocking models and so do pressure regulators and guns with adjustable features. Magazines can be problematic too. If I was going to pick a .25 cal PCP for off grid survival living, I would want maximum reliability; it would be a single shot, bolt action, modest pressure, low shot count, with reasonable accuracy, in a sporter style, which has the fewest moving parts; certainly no regulator and even no gauges. This is my opinion, after owning two FX impacts, two FX Wildcats, and two FX Monsoons, all with never ending problems. The most trouble-free air gun I ever owned was my first, a Sheridan Pump .20 cal. which lasted 61 years with only one rebuild, but that's not a PCP and definitely not a Bullpup.