Actually, oil-based doesn't automatically equal "do not use". I use a number of oils in my mixes (lemon, cinnamon, anise, clove, peppermint, etc.) with no problem. They all mix just fine in pg and from a technical point of view there's no reason to avoid them.
I know that some people feel there's a health issue in breathing vaped oil-based flavors, and it's true that some people have allergic reactions to some kinds (notably, cinnamon, oregano, clove, among others) and should avoid those oils. Outside of that, however, I've seen nothing to indicate a particular health issue. It's certainly never caused a problem for me.
Also, you typically use the oils in a far smaller amount than the flavorings so the amount of oil involved is quite small, and it's hard for me to see how that much oil can cause a problem. When I was a kid manning a deep fryer in a restaurant, I breathed far more oil than I get from vaping flavors.
Anyway, if you are concerned health-wise, don't use the oil-based flavors. Otherwise, do!