Scorpene SSK fitted with NCM would provide the deterrent capability wanted by Poland
Decades after the Harpoon was implemented on ROKS Chang-Bogo-class submarines (Type 209). Shown during the 2008 RIMPAC.
I doubt Poland will buy Scorpene. Type 212 is far smaller and offers better weapons like the tested IDAS anti ASW helicopter missile. The Type 212 is optimized for the shallow Baltic Sea.
http://en.wikipedia.org/wiki/IDAS_%28missile%29
The next thing is crew training. The German Navy knows the Baltic Sea.