Give a kit when entering a region? - Minecraft

I think there aren't any plugins to do so, I'd recommend you to play with WorldGuard-based permissions on the /kit commands.

Cf. Regions flag: allowed-cmds

You can use the WorldGuardExtraFlags plugin to expand the flags you are able to set in WorldGuard regions.

Aside of the normal command-on-entry flag you can then also set console-command-on-entry to execute commands as console when a player enters that region, instead of only commands the player has access to.

I use that to do a few things when people enter the PvP arena, such as disabling all their cosmetics, giving them some temporary effects and setting a PvP rank. It can also set keep inventory and keep exp within a region, prevent elytra flight and prevent items losing durability.