80% would be reasonable. It'd be a mere 20% decrease from what it had, but still 20% better than the best anyone else can get, and free.
80% sounds fine on paper, but the primary reason that Paragon got this range increase in the first place is that its large profile and
very low mobility run counter to the usual high-tech ship focus -- and energy weapons are balanced with that focus on mind. beams aside, energy weapons have significantly shorter range than comparable ballistic assault weapons, because high-tech ships generally have a similarly significant mobility advantage, allowing them to choose where and when to engage enemies of equal size/strength.
Paragon can't do that. its combatstyle is more like that of a semi-station, with great defenses and turret coverage but awful mobility, hence it got a mini-version of the otherwise station-exclusive massive built-in range bonus.
this is also (mostly?) why the ATC does not have a higher-than-normal increase to PD weapons: energy PD is also balanced with the usual high-tech ship focus in mind, and intentionally worse than ballistic PD (generally speaking) in part because the ships that use energy PD are usually much better at just evading missiles strikes. but while Paragon can't do
that either, its strong defensive capabilities more than make up for it.
in short: the range bonus wasn't added simply because Paragon was underpowered, but because its combatstyle doesn't mesh well with the usual high-tech combatstyle that energy weapons are designed/balanced around.
25% higher base weapon range compared to other capitals with ITU is really the minimum of what's needed to counteract this. anything less would again allow ballistics-armed ships to easily outrange
and outmaneuver Paragon.
(it's also not really "free", as the OP cost is just as built-into the stats as the hullmod itself is.)
