Although chastity belt is not mainstream thing now, if it become mainstream for some reason, which kind of improvements would you like to see? I feel I would want to see improvements like these:

Visual looks. Chastity belts mostly look like heavy metal gear. Metal part of chasitty belt at least on front part may be padded (In waterproof material) so it can have variety of colors and patterns if wish. If I'm going to wear it near 24/7 except cleaning breaks, even though it doesn't get visible for others, I'd like it more if it look better. I think that improvement can apply to chastity bra to look more like normal bra or thigh bands so they can look like more of an accessory instead of resembling shackles.
Adjustability. So many cheap knockoff Chinese belts have adjustable design, but in this case, I'm advocating this on premium chastity belts. My idea is that it should have special mechanism that allows adjustment only when it is not worn, and it should only be able to be done by a keyholder (So that can be done only while fitting it to wearer) I think some special layer that comes out and goes into certain slot, or some design similar with ankle monitor's locking mechnism may do its charm. It definitely would reduce hassles with measuring, which would help if chasity belt is mainstream.
Easier to clean design. Currently except chain back, it is kind of hard to do second business with chastity belt, and urine residues can stay on some part of chastity belt on any types. Creating hole that can be used for cleaning it, and also making cable-style back that can be opened up sideways (It may become bit thicker as thick as anal hole style's one (not hole part, but one that goes through hip) but it would be in two pieces that can go sideways) while disallowing cheating the belt would be really nice improvement.
Security in various ways: Locks may not only padlock or radial lock form but also can be controlled remotely, or have wearer app and keyholder app. Wearer app shows rules of wearing chastity belt, such as when it can be unlocked, show tips for cleaning while wearing a belt, or option to unlock it for emergency, which will also let keyholder get notified of it. Keyholder app would allow unlocking the belt (belt would auto lock once worn), schedule wearing time (So in case some breaks are allowed keyholder remotely can set time when it would be unlocked) or see belt's status, whether wearer is really wearing it or wearer has attempted to cheat the belt.
Price: If it is mainstream enough, its production may become more automated and lowers the cost ultimately.