Fiaciki, Mazdki, Hondki, piwko i wódeczka...
Never heard Mazdka or Hondka. They sound ridiculous and strange and may only be used by a person struck with affection. Fiacik was often applied to Mały Fiat (126P). Quite rightly, in my view, as it was so small. I don't think diminutives are overused in Polish.
compare szczęście to the czech štěstí...unpredictable combinations of letters
Actually, the combination of letters cz and sz was an original Czech invention which the Polish had borrowed at the time when the Hus reform of the Czech ortography did not yet arrived. This old Czech transcription has been preserved in the English spelling of the word 'Czech'.
English also uses combinations of letters in the same way as does Polish; these are the 'sh' (Polish sz) and the 'ch' (Polish cz), haven't you noticed?
To a Pole, the more complicated, the better.
Only in your head. We don't feel our language being complicated. Maybe you do, but that's a different kettle of fish.