1Biggun mentioned trying to close up the barrel to gas tube centerline to reduce bending load from the top-heavy bolt carrier. Truvelo claims they did the same to their Raptor variant.
The top picture is a Vektor H5 pump action AK. Notice how they've closed the centerline up as far as practical - the small diameter op rod just misses the top of the receiver where it passes over the barrel. Also note the nifty low profile top cover.
Looking at the small diameter op rod brought to mind the SVD, NDM-85, and Tigr, which use a short stroke floating op rod like some of the AR conversions. That would fit right in with the pump action bits.
The recoil spring would have to be moved to the buttstock, or up onto the op rod, like some of the AR conversions.
For some reason I couldn't find a picture of the SVD's gas system, but here's a Tigr bolt carrier and an NDM-86 gas block...