If i were in your situation, I would keep the Maverick on .30 and leave it as is, and get the impact in .22. My reason is, unless you hunt frequently, otherwise .30 in Maverick will be parked most of the time, ammo is more expensive and way less variety in pellet/slug options. Keep the bigger caliber on the least use gun for the rare occasion for when you really need to sling heavy projectiles.
With the Impact in .22, you have a ton more ammo options to choose from, different weight and shape of the pellets or slugs, you can play with the new gun a lot more frequently, with cheaper ammo so you get to shoot more. The impact is so easy to tune you can practically shoot 11gr wadcutter pellets to 23gr slugs or 25gr AEA pellet right out of the box, at 50+ ft-lb on tap all day all night every single day, without the need to upgrade anything like the power slug kit, heavy liner or any other jazz, those upgrades would be more beneficial for heavier slugs between 27~40gr IMO. The M4 is a super versatile and fun gun to shoot. But If you intend to run the Impact in upper power range above 70~80ft-lb, then go for longer barrel in 700mm, and as you up the reg pressure above 130+ bar, the heavier hammer will be needed.
