Wiatroda,
adjustable mirror block for each mirror, adjustable lens holder for setting the centre hole of the nozzle to the beam path. Flight tubes to enclose the beam path. Safety glasses to suit the power and wavelength of the beam. Possibly a polycarbonate enclosure to surround the cutting head to absorb any stray or reflected beams.
You might want to enquire about the lifespan of the glassware. Our 3KW CO2 glassware is rated for 12000 hours but it costs loads. I dont think the cheap stuff will last very long.

Ian