1:9" twist is fine with the 40gr round nose .22LR ammo. It'll do just fine. Cleaning them is easy as hell, too - at the end of the range trip, pop out the .22LR BCG, slap the 5.56 BCG back in there and let go with about 5 rounds - that will remove all the leading from the gas port, with a quickness. Voila,cleaned. Leading removed.
This is the design that's supposed to be the sheit, right here:
https://www.budsgunshop.com/catalog/product_info.php/products_id/60999/Accessories/Conversion+Kits/CMMG+22BA6E1+AR-15+22LR+25RD+Bravo+Conversion+Kit
If you wanted to get REALLY freaky with it, you could buy a 1:12" twist barrel for it, or even a 1:16" barrel, and make a dedicated gun. If you already have an AR that you don't shoot much, get that kit, a slow-twist barrel, and bam, done. Good 22AR, right there. All real AR15 parts, no weird shiit, and you can still stuff a 5.56 round through it with a BCG change.