Talk me out of the Sigma fp

I've been in the look for buying my first professional camera, and the Sigma fp has really caught my eye. I mean, a tiny full-frame mirrorles that is also an amazing cinema camera? It sounds ridiculous.

I've been eyeing the Fujifilm system for a long while, not because of the film simulations of anything, I just think that the size and APS-C pro-grade cameras are really a good idea. But, when it comes to size, the Sigma fp may even be smaller somehow, and even if I had to expand past the fp I could just go for an S5 II which is in my opinion marginally bigger than an X-T5 or X-H2s.

Now, the one thing I love about Fujifilm is that they are full professional cameras (aside from maybe a decent AF), they have dual SD cards, hot shoe, EVF, lenses, etc. and that is important for me, I am really interested in all kinds of photography, from studio portraits to product photography, I really want to experiment and grow as a photographer and videographer and in my opinion something like a flagship Fuji will allow me to do that.

I say this because looking at other options I saw the Panasonic S9, now, that's a camera with a ton of issues, but the main one for me is the cold shoe; no flash really limits a lot the camera, not to talk about the single SD card which is not great if you are doing professional shoots. I really wanted to love it due to it's size, but it's just made for me I guess.

That's when I magically rediscovered the Sigma fp, which just looks like a strangely perfect camera. Sure, it doesn't have all the features, but you can add them one way or another; the EVF, hot shoe and grip can easily be added to the camera.

I've heard of the bad flash sync, but as a newbie I don't know how limiting that is. I also love the hybridness of the Sigma, tons of people praise it for it's video modes and it's a great photo camera too, aside from maybe rolling shutter. Speaking of which, I think it may be my biggest fear of the fp and the main reason I am considering the fp and not the fp L.

I am afraid that when shooting something like wildlife or sports, or even street, the rolling shutter will ruin most photos. I could get a Panasonic camera later, but I am not rich to be buying full-frame camera bodies like crazy. Speaking of which is also something that I find amazing of the Sigma fp, and that is the L-Mount, which means I could very easily take all my lenses to the Panasonic or Leica systems if I really wanted to, which means that I can really grow a decent lens selection and not worry about bodies being sub-par as I can easily migrate to Panasonic or Leica, which are world-class camera manufacturers.

Another con may be that the fp doesn't have dual SD cards, which I don't love to be honest, but I guess if it really is a great camera in all other regards it is a sacrifice I would make. However, the lack of a mechanical shutter might be the only bad thing I can see in this camera, is there something I am missing? And how bad is the rolling shutter really?

Edit: Forgot to mention that I don't mind the slow AF of the fp, I am used to using terrible AF cameras or manual focus, and I also plan to only use manual focus for video