First, thanks for the laugh. Against advice and your own better judgement, naturally you bought not one but two of these shirts!
I bought a Pleione split neck tunic shirt last fall and have spent a fair amount of time experimenting with different solutions so I don't feel either self-conscious or cold in the neckline. My most successful idea to date has been to layer a black long-sleeved tee under it (the tunic shirt is navy).
I don't yet own white jeans but when I do and can bookend with them, I'll try your solution, which clearly shows the neckline of the shirt. It gets kind of lost in my black under layer.
Oh, and you are SO smart--I'm trying to figure out how to wear a shell OVER a shirt, and while I'm working on that, you go and put one UNDER a shirt with this terrific result!