Should be possible for the 955, at least. Because there is native support for "official" openwrt running on the 955. I did various custom firmwares, based on openwrt, also, but not only, for the 955. However, RMS etc. are Teltonika specials, so its required to implement customized remote access procedure to the 955. Various possibilities here, depending upon requirements. I.e. via http(s), mqtt, VPN ... Also including firmware update OTA, of course, which is required for a fleet of remote devices in the field. I'm a good old German engineer.