The solid-bottomed stock is an advantage in terms of managing action resonance and general handling.
The Trackers, AAs etc aren’t ungainly. The D52/54 are a bit, but that’s because they are huge, not because they are sidelevers.
It’s often claimed that sidelevers have a problem because of the weight of the lever on the side unbalancing them. I have never found that an issue. Far more importantly, the most successful match springers of the 70s/80s (FWB300S, Diana 75) were sidelevers, as were the SSPs that replaced them. So it isnt an issue.
If anyone bar a few of us on here cared about quality springers these days, there would definitely be a gap in the market for a good one. Like a Tracker/Viscount/AA with a much better trigger and, say, an improved BSA-style rotary breech. It ain’t going to happen, though, because it wouldn’t sell at Wal-Mart.