Still haven't used 7U (1U) so hopefully someone else chimes in in that dept.
Function Junction... not sure 'easier Maths'... probably more like poor man's Maths... An objectively lesser capable module. I own both (2x maths... 1x FJ), and while they share similar 'categorical' functionality; just different. FJ sits in a box... in the closet. Might look at Doepfer Dual ADSR or Instruo's Ceis (newly released V2) if you want an "easier" envelope generator. or really any traditional ADSR module.
Too many voices for the size of case is going to be a popular opinion/criticism. BUT... depending on the patch, swapping them out can make sense, so its not like you can't own them. Maybe just keep HP reserved (blank panel for the gap) for a combination of one staple vco and one swap vco. Going to be your call, financially, on that one...
Never tried Ghosts, and probably never will... Modular effects are great to have if you aren't going to be using a computer or outboard/stomp box gear; but I prefer to use in the box/outboard gear fx. Not saying you shouldnt have a module for granular and simple delay/reverbs just to add depth/space. ... I just find 'special' fx modules to never warrant the $; and how could they...? The Arturia bundle is pretty sweet, but I understand not wanting more screen-time added to your day. I have TTA Z5000 -- sounds fine, not special -- MFX -- sounds fine, not special -- and FXAid Pro -- sounds fine, not special. if I kept one... mfx... They are basically akin to a headphone mix for a singer who wants to track with reverb... I run a Metric Halo rig so MIO console gives me zero latency tracking with plugins. That said, I do print Beads reverb regularly.
Also, look into DFAM. Being semi-modular, it can stand next to your rack and create so, so much. Is it perfect? No. Does it have annoying limitations? Yes. Do I still love it? Yes. Using various midi devices really unlocks it... Google dfamThing and mafd. or use a midi controller (keystep) and cv converter.
Enjoy your journey!