Yes and no.
You can do a "simple" integration by creating attach points for bombs or missiles. One of our fellow members did that for a few WWII aircrafts, if I'm not mistaken.
However, these weapons will have absolutely no integration at all with the instruments/commands in your cockpit.
That means you can "attach" laser bombs to your plane, they will show externally, but you're not going to get any laser targetting display in your MFD in the cockpit. The bomb will just drop when you press a button on your joystick.
Same with missiles: you can attach some A/A radar missiles, but they will not react to anything you do on your radar MFD. You won't get anything on your HUD either.
This system is "nice enough" for simple weapons like on WWI and WWII aircraft (just guns and bombs). But for modern aircraft with electronic weapon systems, this is really not suitable at all.
EDIT: I was speaking about integration by external people, not by the aircraft maker.
Of course Virtavia *could* make a proper integration of TacPack. A proper integration means modifying the cockpit to create/integrate new systems and buttons/screens that were not modelled before. Only the addon aircraft maker (Virtavia in this case) can do that. Not us simmers.