How to add uart function to light control client demo at nrf5_SDK_for_Mesh_v0.9.2-Alpha

I've run an mesh example of light control with three 52832DK board.There are some question. [1]Now i want to add uart function to the example,then i can send msg without buttons.please gave me some advice about how coexistence with other Nordic SDKs. [2]In the Header file "simple_on_off_common.h",there is a message format for the simple onoff set message:simple_on_off_msg_set_t.The struct have only two byte,on_off and tid.if i want send more msg from client to client, can i add other parameter into this struct.if yes,then how many byte can add.