Thanks for the kind words everyone!

I experimented a bit with Pasta's script for reprojecting, here are the results:
Click image for larger version. 

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Sample 1:
Workflow:
- Straight up reprojection, either with Projectionpasta or GProjector

Result:
-Basically no difference between the methods, noticeable choppy "stretch marks"

Sample 2:
Workflow:
- Scale resolution up x2, reproject with Projectionpasta, then scale back to original res

Result:
- Eliminates the "stretch marks", though also creates some extra blurring (especially noticable along the coastline)

Overall, I think I much prefer the blurriness over those annoying stretch marks (that are extremely hard to get rid of, I might add). The coastline is easy enough to restore and I do that anyway when reprojecting.

@worldbuilding pasta:
Personally I found Projectionpasta quite quick, even with x2 res (11600x5800). Huge thanks for creating such a useful script, breaking free from GProjector's resolution constraints is a big step up for me.