Hi Naugrim,
First I thought "what a small system" but having a good look at it, for the fact that's so small, it's quite complete. You got your VCOs, LFOs, filters, envelopes and VCAs/mixer. You could consider a linear VCA for CVs, a logic module might come in handy and the obvious as you mentioned yourself already, a sequencer and a few effect modules.
Regarding the 1U definitely look into Audio input/output in combination with (if you go for it) Intellijel 7U case to make sure you got everything you need. Or are you going to do that via your computer too? But you mentioned that if you are not connected to a computer, so I still would consider that (audio input/output module I mean).
It's not a huge system, rather small, so don't expect wonders from it, however you got the most basic modules covered. So get experience with it and with that experience then decide how you are going to fill up the second row and that second row will be faster full then you might think or want ;-)
Good luck with the planning and kind regards, Garfield Modular.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads