The stronger cinnamon flavors, not so much the flavors with a touch of it, will crack or melt polycarbonate tanks. So yes, you can dilute them to an extent, but you'll want to experiment a little about the level of dilution.
Generally, it's the highly acidic flavors that do this, including some cola flavors and most (but not all) citrus flavors. I don't believe it's relevant whether or not they are oil based. I know from experience that at least one pineapple flavor does it as well.
There is an old, very long thread here that I should have bookmarked, keeping track of which flavors have caused problems. You can likely find it with some searching since it is updated (or at least it was) pretty regularly.
Other than glass or metal tanks, plastics high in polypropylene are resistant to this problem. You can tell them by their foggy appearance as polypropylene is not as transparent as polycarbonate. It is also softer and high PP tanks and cartos feel less hard than pure polycarbonate ones. Gotvapes says their Vivi Nova 2.5 tanks are crack resistant, but I can't vouch for that because they appear to me (as does the rest of the tank) to be absolutely identical to the 2.0 version and I haven't tested their claims. OTOH, I have used some cartomizers with the high PP plastic formula and it definitely holds up to high acid juices.
There is also at least one tank out there made from delrin, which is impervious to anything. The name escapes me but maybe someone else can chime in. The problem with that tank is that is not very much more transparent than metal, although it does have a "fuel gauge" of thinner delrin that can be semi-transparent under the right lighting. In fact, I think the name of that tank might be "Fuel tank".