I'm doing an AngelBob run with this mod, and I'm concerned that I'll want to put two 4->4 pipes in places where they want to connect, but I don't want them to. Is it possible (and/or a good idea) to add 4->1, 4->2, and 4->3 underground pipes?

(I haven't run into a place where I need 4->(not 4) pipes, so I may just be borrowing trouble.)

Usually the 1->whatever pipes work quite well. I can look into it if you would like.

2->whatever would be pretty useful, I've been having a lot of adjacent buildings that those would work well with. I've been using 4->4's but the other axis on the 4's are trying to connect to things that I don't want them to connect to when a 4->2 would be perfect to pass it 'along' the axis. :-)

Also, any chance of higher tier's of the 4->4's too? ^.^

i would like this too

It's common to want a 2->2. For example in a large array of the same kind of machine taking the same kind of fluid input, it's convenient to have two rows share the same pipe by having their inputs face opposite directions. The obvious thing to want in this situation is a 2->2 pipe. But when I would want a 2->2, I just use a regular pipe connected up to a 1->2 instead. Other than that I find that a 4-4 is at least topologically sufficient, but the fact that there is no red or blue 4-4 makes it rather impractical to try to use them anyway.

I'll look at 2->2.

I'm also looking at doing those T2 and T3 4-4 pipes like you mention. Shouldn't be super complex at all.