Pistols as melee weapon will surely be weaker than other melee weapons, otherwise it makes not much sense to use normal melee weapons.
Sawyer specifically says they'll be useable as clubs, which suggests that they'll have the same stats as clubs while the modal is activated. You might still be right if the enchantments on pistols are inapplicable at melee range, which could be the case for stuff like increased reload speed. That being said, the enchantment features for pistols from Pillars 1 are easily applicable to melee weapons as well and I wouldn't expect that to change in Pillars 2 overall.
I'm all for pistol whipping myself and think the option's missing from entirely too many games, but if each weapon gets only one modal, then this seems a bit overly niche compared to stuff like the Savage Blows modal for great swords and Vulnerable Strikes modal for estocs, both of which make you better at using those weapons in ways you probably intended to use them in the first place. If any firearm got a modal based around quicker reloads I'd expect it to be the pistol, but alas...
Well, after some reading I wound this: https://en.wikipedia...ki/Pistol_sword
Nice catch, but they might fall a bit outside of the intended technological period, since a lot of those are 17th or 18th century and the ones that aren't look like they'd be unique daggers or swords rather than pistols. What's more problematic from a design perspective, I suspect, is that a lot of those look like they'd require unique handling and/or attack animations whatever weapon type they're associated with.