I had the exact same idea, finally found some rhubarb flavoring now available from my usual supplier. The only one available is from Inawera, so I added to cart right away and should get it in by next Monday. Here is my plan of attack, feel free to adjust and let me know how it turns out.
Filling
TFA Ripe Strawberry 5%
INW Rhubarb 1.5 - 5% (will need to test this flavor when it comes in, but INW is pretty potent usually)
Crust
FA Cookie 1%
TFA Acetyl Pyrazine 0.5%
OR
TFA Pie Crust 1 - 1.5%
Topping (cause I love a lil' ice cream on top!)
TFA Vanilla Bean Ice Cream 3%
I'm leaning toward TFA's strawberry ripe because it has more of a cooked strawberry taste than most of the other strawberries out there, more realistic and not as bright. You could use another SB and throw in 0.5% FA Liquid Amber in there to "cook" it, but I'm out of amber so I'll have to do with what I got.
Hope that helps!