I have been hesitant to get into 5.7 and the main reason is the reliance on factory ammo as I do not view this as a cartridge worth the trouble of reloading. Right off the bat there's an issue with the cases having some special laquer or coating on them that requires special cleaning, then FN uses some sort of adhesive on the bullet to hold it in place and those two things alone already turn me off. Add to them the cases themselves don't last, they're pretty much good for one reload and after that they're toast, if not downright unsafe to use again.
The powder charges need to be exact, which means you have to weigh every charge as no powder measure is going to throw an exact charge 100% of the time.
The bullets themselves would all have to be FMJ, which means added expense.
Even if you did go through all the trouble and had a process down and were all tooled up, at the end of the day what does the 5.7 give you something else doesn't and at an easier means to reload? While it's not available from anyone other than Rock Island, the .22 TCM offers several advantages over 5.7, the main one being higher velocity and can be made from cut down 5.56 or .223 cases, which are super easy to acquire for free at any range in the country. Sure, the .22 TCM pistols can't hold 30 rds like the 5.7 can, but I doubt anyone will ever need a 30 rd mag in a pistol for any serious defensive situation.
If the idea is reloading a low recoil, but zippy caliber, then .22 TCM and 7.62x25 are better choices. Even .30 Super might be a better option, I'm sure there are some pistols in .30 Super that will be able to run with a low power reload.