Like Gis and Ali, my Playmoworlds are more fantasy than reality, which allows me to mix and match pretty much anything I like. For me it's too much trouble, and too potentially expensive on spare parts, to do otherwise.
e.g. The Roman auxiliaries add-on packs had greaves when they should have sandals. To replace those I bought before I realised would now be costly. The redcoats wear black riding boots, when white trousers with black shoes or ankle-length boots, grey ior black trousers, or black trousers with a red side stripe, would be more accurate depending on your period. Cheaper and easier to stay with the original figure and have done. The list could go on forever.
It's the coward's cop-out, but life's too short to sweat the small stuff.