  We study a model with an exotic new sector strongly coupled to the Higgs
boson, in which supersymmetry is introduced to protect the quartic coupling
from a large running and avoid potential vacuum stability problem. The
fermionic components present vector like mass terms, through which the Higgs
diphoton decay branching ratio can be tuned. The bosonic components trigger a
strongly first order electroweak phase transition. We find a large parameter
region of effective Yukawa coupling $y\gtrsim2$ and mass parameters $m_f\sim
m_s$ of a few hundred GeV, that can simultaneously accommodate the diphoton
excess and electroweak baryogenesis, without vacuum stability and electroweak
precision measurement problems.
