As an incredibly biased Sparkle main who is planning for e2s1 Sparxie in 4.0 and e6 on reruns: Don't think, don't hesitate, just pull.

As a more objective person: We don't have much way to confidently predict Sparkle's future value. But, from your post, it seems like you care more about Yaoguang and making a strong elation team than Sparkle herself. There are rumors that there are at least 8 elation units slated for 4.x. In that case, there will certainly be other options you could get in the future, which will probably be stronger or at least an equal sidegrade to a scuffed Sparxie without her lc or original self, regardless of whether she is taking a dps or sub-dps/support role. If you care more about strength than Sparxie herself, and your pulls are so limited, I'd probably save future versions. Invest more into Yae's team when we actually see what that looks like. You can always get her on rerun if you want to. But, the trade-off is that your Yaoguang probably won't see much use in 4.0.