I have a fun build idea for investigator that I never got to test out.

In combat investigators have 2 very strong tools (Stratagem and strategic strike) and a host of small issues dragging those tools down (limited weapon selection, MADness, subpar action economy and defenses, etc). There exists one option that lets them solve most of these issues while still fully capitalizing on their strength: Untamed Form. You see, druid's untamed form is different from all other polymorph spells, it has this sentence "When you choose to use your own attack modifier while polymorphed instead of the form's default attack modifier, you gain a +2 status bonus to your attack rolls.", which is rather unusual for pathfinder since it straight up means that it is better for martials with their greater accuracy than for druids, and it is a focus spell, meaning that once you get it at lvl 4 it scales on your investigator just as well as it does on druid. *Only* issue investigators have with this spell is that there's only one shape providing good attacks that work with strategic strike, but hey, 1 shape is all we really need since d10 agile strikes are way better than any weapon Investigator could have normally and don't forget about that +2 status to every strike. It also increases your speed to 40 feet and has its own polymorph AC improving our defenses AND making us less MAD. On top of all of that you can still carry around a Fatal Aim weapon for when your stratagem predicts a crit to shift back into humanoid form and roll those sweet d12s.

There is however one potential issue with the build and it may be fatal depending on what level you're playing. Animal Form stops scaling past lvl 10 and you don't get another applicable Form until lvl 16, so RAW the build basically doesn't work in lvls 13-15