Possibility to use high intensity secondary beams at the SPS M2 beam 
line in combination with the world’s largest polarized target, liquid hydrogen, 
liquid deuterium and various nuclear targets create a unique opportunity
for universal experimental facility to study previously unexplored aspects 
of meson and nucleon structure, QCD dynamics and hadron spectroscopy. 

High intensity hadron (pion dominated) beams already made COMPASS the 
world leading facility for hadron spectroscopy and  hadron structure 
study through Drell-Yan production of di-muon pairs. High intensity 
muon beams, previously used for unique semi-inclusive and exclusive 
hard scattering programs, make possible proton radius measurement in 
muon-proton elastic scattering and and further development of polarized
exclusive hard scattering program. 

Upgrades of the M2 beam line resulting in high intensity RF-separated 
anti-proton- and kaon-beams would greatly expand the horizon of experimental 
possibilities at CERN: hadron spectroscopy with kaon beam, studies 
of transverse momentum dependent quark structure for protons, pions and 
kaons, precise studies of nuclear effects and for the first time measurements 
of kaon quark-substructure.