the texture is included in a .u file and if I update it, it will cause version mismatch!
As far as I remember the "version mismatch" error occurs only in two cases:
1) when the client already loaded an incompatible package with the same name.
2) when the client has received a compressed package that had the same name and size as some incompatible package in the client's cache.
In the first case, the user may try to unload the mismatching package (along with the current map) by means of console command "disconnect" and then reconnect to the server.
In the second case, the user may enter the game after removing the corrupted file from his cache folder. A server owner may prevent such troubles in two ways: by disabling package compression entirely (the most reliable way) or by modifying the size of the package so that it would not match the size of any other existing package with the same name.