@Alan de Enfield, @Tony Brooks, @WotEver,
thank you very much for your quick answers, Tony your website seems full of ressources, a shame not to have found it before !
Ok so for the solar panels, I think we will go for the corner solution If I well understood, as our battery bank is 24V and we have the MPPT, connecting the panels in series is quite the best thing to do. To fix the installation, we've read good feedbacks about magnets, and to go through the roof, we were hesitating between using the pigeon box (but may be difficult to waterproof) or drilling (but that we would have preferred to avoid).
Talking about the generator charging the batteries, here is the schematics of the inverter (yes this is a combi, sorry for the misunderstanding). For now, I think the shoreline is connected to "AC input", nothing is on AC output 'power' (AC output "short break" is meant to reduce battery power consumption is no loads, I think but not sure). Now when selecting the charge mode, the inverter don't see anything (the AC input light is off, all lights are off...), so I suppose only the shoreline is wired to the AC input. So I could eventually plug here the generator, that's nice to hear ! But so much wires around the generator :S
And so for the position of the MPPT, in parallel of the inverter (using the same battery fuse 4)? If the battery bank is 24V, I read somewhere that a there should be somewhere a charge controller, wired to both the alternator and the inverter "battery terminals" ?
Thank you again for your advices !