  Novel considerations are presented on the physics, apparatus and accelerator
designs for a future, luminous, energy frontier electron-hadron ($eh$)
scattering experiment at the LHC in the thirties for which key physics topics
and their relation to the hadron-hadron HL-LHC physics programme are discussed.
Demands are derived set by these physics topics on the design of the LHeC
detector, a corresponding update of which is described. Optimisations on the
accelerator design, especially the interaction region (IR), are presented.
Initial accelerator considerations indicate that a common IR is possible to be
built which alternately could serve $eh$ and $hh$ collisions while other
experiments would stay on $hh$ in either condition. A forward-backward
symmetrised option of the LHeC detector is sketched which would permit
extending the LHeC physics programme to also include aspects of hadron-hadron
physics. The vision of a joint $eh$ and $hh$ physics experiment is shown to
open new prospects for solving fundamental problems of high energy heavy-ion
physics including the partonic structure of nuclei and the emergence of
hydrodynamics in quantum field theory while the genuine TeV scale DIS physics
is of unprecedented rank.
