For years, one of my main jobs was tank ammunition, much of which had sabots. The speeds were somewhat higher than airguns can manage, Mach 5 to 6, but many of the problems are the same. The first problem is getting the sub projectile central in the bore, which requires a high degree of accuracy in the sabot manufacture. Then there is the question of the barrel twist rate. Say you have a .3 calibre gun, and you want to fire .22 rounds in sabots. The twist rate for the barrel will need to be the twist rate needed for a .22 projectile, not a .3. This will make the barrel less optimum for any .3 ammunition you may want to fire, so you may then end up only able to fire sabot rounds with acceptable accuracy.
Next, as has been touched on, there is the question of separation. This has to be as close to perfect as possible. Millions of dollars were spent studying sabot separation, so the chances of someone new getting the design right are roughly zero. Bullet like sub projectiles usually use pot type sabots which come off as a single item. These are easier to design than the separate petal types, which are more difficult to get to separate cleanly. There will usually also be a slot in the base of the sabot which engages with a tooth in the bottom of the projectile, or the other way round, to provide spin transmission to the sub projectile.
Finally, suppressors are not a good idea with sabot rounds. You can get away with it with a pot sabot, but probably not with a petal type sabot.
