For fighting Hijacker coms, I used a Battleship (hull IX) with Improved Shields. No weapons, but with an AES:MAU ratio of 2:3. For example, 10 AES-M for every 15 MAU-M. If you had higher level AES, you could double up (for example, 5 AES-MM is the same as 10 AES-M). This is not the case for MAU, though, as MAU suffer from fatigue, so a few smaller MAU may be better than one big one. This combination tends to work for anything unless you are very unlucky in encountering 5 or 6 pirate ships all with improved armour. In that case, MAU are sometimes not enough – or the battle would take longer than the 60 days.
Your maximum ship power for collecting and fighting hijacker missions is around 150 million. If you go any higher, you risk not being able to fight the ships within the maximum 60 days, which will give you nothing.
To collect all the POW, I'd look to have at least an ACB-MMMMMM on board (or 3x ACB-MM). A Safety Override (SO-LCCVII) is also useful.