Thanks for making a really cool mod!

(Can see Fundamental Comprehension tech)

Stack Combinator (tech uses vanilla science packs)
Statistics Combinators
Utility Combinators
BIG LIGHT (since miners are modified, the lights on miners are sadly not affected by the mod)
Shortwave for 1.1
Crafting combinator
Circuit HUD v2
Magic lamp
PE Stringy Train Stops Redux
Pause Combinator (my mod)
Recursive Blueprints+
Remote Switch
Santa's Nixie Tube Display
Schall Circuit Scaling
Spidertron Logistics System

These need special attention to how the Ultracube is handled but would be nice to try with anyways:
Memory Storage (makes no sense to put the singular Ultracube in memory storage but there's a lot of buffering in Ultracube so the mod would be an interesting combo)
Fluid Memory Storage
RE: Storage Energistics

Yeah, as noted mods that add techs or recipes will need dedicated compatibility code in general. That's quite a list but if there's any you particularly would like to see supported let me know. Mod authors can also add compatibility in their mods (I'll add more details about this soon).

The mods

PE Stringy Train Stops Redux
Recursive Blueprints+
Crafting combinator
Stack Combinator

seem like the mods I would use first and can't really work around not having.

Thanks!

RB+, SC and Santa's NTD compatible! Thanks!

PESTSR and CC to go :D

I was first thinking that Memory Storage and Fluid Memory Storage (MS+FMS) might be too OP, but after considering it some more it might be that their considerable power in buffering and increasing belt/train capacity might not actually compromise the challenge of Ultracube really. Bottlenecks in Ultracube are more about the logistics complexity and the challenge is the combinator circuits required etc. And MS+FMS just adds more circuitry needed to not end up deadlocking because you are doing infinite buffering or don't have adequate control over how many memory sticks each requesting station ends up with etc.
So MS+FMS together with Ultracube might actually be a good fit both with the strengths and the challenges those mods introduce. But I'm still just building my new base for 3rd card production. So I'm interested in hearing what you think.

If Ultracube doesn't have logistics bots then I'll retract my requests for Spidertron Logistics System.
I don't know how easy RE: Storage Energistics is to use at large and diverse scale. Might be too simple. Might actually need logistics bots because:

Is this intended to be a bot network replacement?
Not exactly, while it can largely replace the logistics network, it can not fully replace it, and is designed to work with it.

DARK: Storage Energistics is a more updated fork. But I think I'll try this mod without Ultracube and retract my request for compatibility for now for the "Storage Energistics".

I do have an idea for a similar mod though that could be really fun, with a similar basic idea that Ultracube has. The idea is transfering items box to box like "Storage Energistics" through circuit network, but with only one central controller (like Ultracube as 1 ultradense utility cube) that can transfer items from any connected chest to any other. But it needs explicit commands with source and target id or position and maybe items and counts etc. Or maybe it would just swap the contents of 2 chests by position, so if you don't know the contents you might just send the items back in the opposite direction you intended. So it would require the computations to compute all logistics and the communication network so that the central controlling circuit can do accurate transfer commands. Which could get really complex but interesting. So it would look like it would work like logistics chests but with instant transfers in bulk without the need for bots, really powerful. But in reality would be way harder to use for anything with multiple types of material.