Building H-bombs and advanced warheads is very much possible for Pakistani scientists and engineers. Now Khushab-1 and the under construction K-2 and K-3 reactors are a source of tritium along with plutonium.
It was Munir Ahmad Khan's vision that Pakistan should be able to develop the technologies needed to build thermonuclear and tactical warheads that use plutonium as fissile material and other warheads that use a mix of both uranium and plutonium, and that is why Khushab-I was conceived and initiated by him in 1985. He had also set up a tritium purification/recovery facility at the Khushab Nuclear Complex site by 1987.
Now tritium is necessary to boost fission warheads and build thermonuclear weapons as well. Building a H-bomb design is very much possible for Pakistan. Dr. Samar Mubarakmand told the Urdu Newspaper Jang on 15-05-1999, that "if needed Pakistan could build and test a Hydrogen Bomb".
Dr. NM Butt, former DG (PINSTECH) in 1999 said that Pakistani scientists could also build a Neutron Bomb if needed.
Basically an advanced H-bomb could be built once a workable bomb design has been constructed. PAEC scientists have had experience with developing nuclear weapon designs since 1978 when DTD had its first bomb design ready. Thereafter from 1983 onwards, 24 cold tests of different weapon designs were successfully conducted by PAEC till 1990 and this continued in the 1990s as well. Dr. Samar in his Speech given at GC Lahore in November 1998 has said that PAEC theoretical physicists can develop a new weapon design every 2-3 months.
This implies that the technical expertise for advanced weapon design development is well in place which is also experienced with other aspects of warhead development such as electronics, computers, diagnostics, high explosives, machining and metallurgy, and mechanical engineering.
PAEC has been and now NESCOM is building advanced compact warheads, for tactical use, for ballistic and cruise missiles. After Khushab-I went into operation in 1999, Pakistan now has sufficient plutonium and tritium to build advanced compact warheads. It will also result in economy of fissile material, i.e. the more sophisticated the design, the less the PU needed for the bomb.