I think you made a good decision with the changes.
Recently I am thinking to switch my 909 Hats for the Erica Cymbals. They are super versitile and produce very decent hats as well. I use the Modbase Kick for the booom but if I did not have it already I would probably go for the Entity Kick.
Seriously get a DivKid RND STEP. It gives constant modulation and is great to keep voices alive, especially drums imho. It is doing its thing in every patch and track I make. Attenuators help keep it in a reasonable range (Quad Atten or Junction, but you might wanna go for a 1u version).
I reconsidered one of my advices. Pamelas Workout is great , but it is a complex module that needs deep diving to use it imo. Since this is your first system, I would highly recommend cutting complexity where possible. Might wanna go for a Batumi II or a 4ms pingable quad LFO. This is a very personal opinion though.
When I bought my first system I was pretty overwhelmed (though it took me years to actually acknowledge that). Every module has so much potential and funktions, endless possibilitys but I always ended up doing the same things or I got stuck at complexer and menu heavier modules and it interrupted my flow.
My philosophy now is to avoid menus and have everything at the surface and the tip of my Fingers, it is immidiate and more fullfilling. Pamela is great, especially in smaller systems, but it might be a brick in yours for the start.
You dont need the scope :) Its just a gimmic imo.
A Midi connection I recommend strongly if you plan to arange and edit in the DAW so the DAW can be your master clock.
Most importantly: A system is never finished. There will be constant change so do not be afraid to buy th "wrong" module, you can always sell again. You will find your prefrences and those will change with time. Enjoy the ride :)
That said, I am curious to hear it when its done.