There is one mod that I used to play with before I got into modded MC that had some incredibly useful features that may be right up BC's alley and are unlike anything I've seen since, and it is WorldEdit.
I think that features similar to those in WorldEdit or MCEdit could be implemented in BC by way of the Urbanist block that I heard of a while back and a swarm of Robots. As it is, you can do some of the things WE can do with the Filler, but you have to go to four different corners of the region to fill/clear/whatever, place landmarks, place the Filler, choose the mode, and supply it with energy and blocks (but that's to be expected, since this is supposed to be Survival Mode friendly). With WE, it's just click here, click there, //set air, done. I could see the Urbanist replicating that to some extent- go into 3rd person view, click here, click there, type a command or choose action from a GUI, unleash swarm of robots, done.
The recent re-implementation of the Builder and pathmarks provides a way to replicate //stack, //copy, and //paste, but once again, you have to manually set the volume to copy with landmarks, place the Architect Table, give it a blueprint, place a line of pathmarks for where you want to copy the structure, and place/power/supply the Builder. I could see the Urbanist reducing that to click here, click there, enter command or click MCEdit-style GUI to copy that volume to an actual physical blueprint stored somewhere, and click a couple more times to unleash the robots to rebuild it somewhere else.
I guess what this could all boil down to is a way to have the Urbanist replicate the functionality of all the BC machines that interact with the world (pump, filler, quarry, builder, floodgate, etc.) without actually having to place those blocks in the world. Rather, all you'd need to do would be to tell the Urbanist where to do the things that those machines do, and it'll do it for you. Of course, there would be a lot more power, time, and shuffling of items that WE simply doesn't need to worry about, but so long as there's a way to upgrade the robots so they fly faster, can carry more than one item at a time, and are fireproof, I don't think that'll be an issue.
Also, the polychromatic pipes of BuildCraft do have one thing going for them- they're considerably easier to configure, once placed in the world, than anything else out there. Yes, you may have to carry around a dozen different types of pipes, but at least there's little to no messing about with GUIs unless you're using gem-based pipes. Need to extract items? Wooden pipe, redstone engine, redstone torch, done. Need to extract faster? Use a sterling engine or an autarchic gate. Don't want this pipe line to connect to that one? Make one with cobble pipes and the other with stone, or put a plug in between. EnderIO conduit GUIs, I've found, are particularly annoying to deal with.
Also, people don't seem to realize this often, but stone pipes are cheap.
Maybe the cost of diamond pipes could be brought closer in line with that of other mods' sorting mechanics (XU sorting pipes, TD filters, EnderIO filter items) by having each pipe only require an item that's, say, a 4th or 16th of a diamond, and/or is dropped in addition to the usual drops from diamond ore when mined with a particular tool (or TiCon tool upgrade? Hmm...). It's just annoying when you're trying to set up an early-game sorting system and you have to use two of your first few diamonds to do it.
There are only a few minor suggestions I could make with regard to the pipe system:
1. Add some sort of simple always-on autarchic gate that's not much than a redstone engine in the tech tree. I don't mind if it's a few times as expensive than the RS engine, so long as I don't need the diamondspam that is an assembly table.
2. Make it more obvious what happens when you have multiple "Energy Pulser" conditions active in an autarchic gate. For those who don't know, each active pulser beyond the first doubles the number of items extracted at a time- so having seven pulsers active in a diamond gate will extract a stack of items at a time. This could be done through an in-game manual or noting this behavior in the Pulsating Chipset tooltip.
3. Some simpler way to create setups that won't drop items everywhere. I know that this can be done with pipe loops or gates, but such setups always seem overcomplicated and un-compact. This may actually be very simple to implement, at least for some setups- just make the clay (insertion) pipe bounce items backward if they have nowhere else to go, and make the wooden pipe insert items coming into it into whatever block it's supposed to be drawing from or just buffer the items and spit them back out the next time it gets an RF pulse. More complicated setups might require a new pipe (or gate feature?) that routes items based on which direction they're coming from. I have two ideas for this:
3a. Give each end of the pipe a different color, akin to diamond pipes. In the pipe's GUI, you can specify which direction items coming from each direction should go, i.e. send items coming from the north eastward, send items coming from the east southward, etc. If items cannot go in the specified direction, for whatever reason, the pipe reroutes them as if they just came from that direction. So if, in the above example, there was either no pipe or a full inventory on the south side, items coming from the north would just go eastward. Failing that, they'll just drop on the ground.
3b. Basically a restricted version of the above where all the inputs except one direct items the same way, and items that come in from that direction exit in a different specified direction. This could be handled with a wrench- right-click to set the default output, shift-right-click to set the output for items that come in from the default output.
4. Some way to direct items in transit based on redstone/pipe wire signals would be useful occasionally and is not to be found in any other mods that I know of, but sounds like something that already exists and I would find it if I did a little research.
5. Add a wood/gold hybrid pipe that accelerates items as they're extracted. Or just make the emerald pipe do that.
6. VERY minor: Change the textures of the wooden, iron, diamond, emerald, etc. pipes to be somewhat more transparent. Mostly because it's really hard to see the items a wood pipe is extracting as it's extracting them when there's a gate on it; putting a transparent stripe down the middle of the opaque side should fix that.
I would also add that it can be difficult to remember which pipes do what, but I've noticed that the tooltips have become much more informative. Props to you and your team for that.
