There are 2 existing mods which should do what you’re looking for:
the first is the Super X mod found at Kodi4444's workshop mods or the Steam workshop. It gives you a config file so you can set all hearthlings to any range of stats you like – so you can make them all 4/4/4, or like 3-6 with a maximum of 12 if you want a little bit of randomness but still reliably no “bad” hearthlings.
The other mod is BEAM, which can be found here at Beam - Hearthling Stats Customization or again on the workshop. This lets you pick out not only stats, but also traits – perfect for min/maxing “super hearthlings” specially build for their job, e.g. make sure your farmer or cook has Green Thumb and your soldiers have Glutton (for extra health!) It only works on the starting 6 hearthlings sadly, but it allows you to start the game with your “perfect set” of hearthlings regardless of what your initial roll is. Remember to tick “unlock selections” if you want to be able to freely move attribute points and go over their original total (by default, the mod won’t let you increase the total skill count unless you’ve unlocked the selection.)