Oh indeed, balcony systems are small and limited — the constraints that led to them are: (1) DIY-safe, (2) useful for rented apartments (limited window or balcony fencing space, may not be allowed to fix something to an exterior wall).
I'm not sure if you're allowed to just resistively dump an off-grid PV system into a resistive heating system, but I guess if you did, you could indeed save on the cost of the inverter.
efficiency of no MPPT is around 10 percent lower then with MPPT system so no issue. 2000 watt is maybe max what you can have on balcony - physical size, and 2000 watt inverters are like 20 $. well connecting anything to grid is/should issue, offgrid noone cares.
You might be able to hang an additional balcony system out a non-balcony window or something, or just keep it inside the window. Less insolation, but maybe not so much less that it's unprofitable.
I believe that even in Germany you can connect a low-voltage solar panel to a battery or heating element without any licensing approvals beyond CE. Low-voltage wiring poses much less risk of electrical shock and is consequently exempt from most safety regulations.
I'm not sure if you're allowed to just resistively dump an off-grid PV system into a resistive heating system, but I guess if you did, you could indeed save on the cost of the inverter.