Welcome to Eurorack.
You're buying a case and completely filling it. You'll have to buy a second case if you want to expand. I hear what you're saying but the reality is that most people want additional functionality once they get some wiggle-time in with their modular.
For the price, I prefer Intellijel's old 4U 104HP case... but they stopped making them. If you can find one of those 2nd hand, I'd recommend pouncing on it.
For the size of your case the Metropolis is just too big. It's nice to have a sequencer in the case. But you'd save money and do better buying something like a Keystep Pro or a Beatstep Pro. The Metropolis can't sync to MIDI so whatever you create with it won't sync to anything else without some more modules... but you don't have the room. If you really want a sequencer, I'd look for something smaller that has the ability to sync to MIDI.
You need mixers. You have none. The Intellijel VCA can sum two inputs. But there's no way to control the proportions of each signal. The 2HP VCAs do not sum according to the manual.
There's no LFO in the set-up. I'd think about that as LFOs are pretty common in most synth systems.
Overall... I think you COULD keep this case to make a basic system if you replace the Metropolis with another sequencer (internal or external) that has MIDI and then reclaim the saved space for additional modules you may want or need. Small systems are much harder to put together than larger systems as you're trying to balance space with practical functionality. The value of a small system is usually so limited that they are no more capable than a plug-out synth like a Behringer Neutron or a Moog Mother 32. Honestly, I'd recommend buying a Moog Mother 32 rather than what you have here. Less expensive and more features.