I have a Multiplus-II GX 48/5000/70 for my household together with an MPPT RS 450|100 and a SunnyBoy.
Did a lot of programming in Node-Red and never had the idea that I was missing options.
Just my two cents 
The whole setup can run offgrid if necessary.
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The MP2 and the Multi RS create a grid onnAC-out while offline. Grid tied inverters like Fronius, Hoymiles etc must implement frequency shifting, which is used by Victron to throttle power source while discounted from grid.
Search for Fronius grid code MG50 with Victron for off grid operation.
I do not know if a generator in AC-in can be combined with frequency shifting. In that situation control of Fronius via ModBus might work like connoted to the grid.