"My theory is to write a standard simple call script that refers always to Server side logic".

Any server side business logic procedures can be used in validation expressions, used in {...} macros, called using Lianja.evaluate() or setup as remote procedure calls as described in an earlier forum post which has some code examples:
http://www.lianja.com/community/showthread.php?2998-Lianja-v2-0-Beta16-improved-Client-Server-integration

Building Web and/or mobile Apps requires a separation between the UI presentation and the server side business logic.