Feed switch 2 systems

[OldBoathouse]

Hi, We have commissioned a professional firm to install Solar system. Originally, we asked for separate feed for flat upstairs and shop downstairs but the 8 panels each would yield not enough for either. I have suggested installing a single array of 16 to a big switch that I could direct feed to shop inverter in summer and flat inverter in winter. The installer is telling me that this is unheard of and its experts scratching heads on how. I'm thinking, it's a switch, how hard can it be? Anyone tell me why this is difficult or point at someone who's done it before please.

16 panel array - isolator - switch < (shop inv) - (shop consumer panel)
                                  < (flat inv) - (flat consumer panel)

Andrew