Solution : https://service.sap.com/sap/support/notes/207101 (SAP Service marketplace login required)
Key words : 
call function 'scp_mixed_languages_1_switch'    exporting need_lang = data-langu, proposal           set locale language data-langu, command set locale language space, set locale language data-langu, command set locale consumes, data-langu >< sy-langu, data-langu = sy-langu, code    call function 'scp_mixed_languages_1_normal', set locale language space, additional key words mdmp
Related Notes : 
       
| 745030 | MDMP - Unicode Interfaces: Solution Overview | 
| 73606 | Supported Languages and Code Pages |