I'd be more inclined to go with rocket-assist rounds myself. Increase range, same payload. Only rule changes would be larger scatter as range increases.
where are you putting your propellant? You'd still be looking a either a reduced payload, or increase in shell weight. (Sometime over a decade ago, when these boards were a few iterations back, I actually suggested RAP or 'rocket assisted projectile' rounds-the need to carry propellant meant a reduction in shell weight there as well.)
Thing is, I don't think Saboted rounds would necessarily increase effective range outside of specialist environments like vacuum, because saboted rounds tend to be MORE vulnerable to wind drift on high-angle applications. (Lower mass to the surface area exposed, vs. higher sectional density of the projectile vs. lateral surface exposure and lower mass.)
Wind drift is influenced by your total mass vs. the exposed surface area. Long, needle-like forms tend to be more vulnerable to wind drift than shorter projectiles of the same (Or greater) mass. Artillery shells stop accelerating as soon as they've left the barrel-they're flying on inertia to the target (except with a 2nd stage rocket boost), and at apogee they start going down again because gravity has overcome velocity (they start accelerating again on that down-slope, but it's at or near terminal velocity in atmosphere for a given planform of projectile.)
Generally, sabot configurations are about relatively short to medium-range PRECISION. (aka making the shell 'shoot flatter' to hit, say, a moving target).
