Maybe an extra upgrade like the b(e)acon bases?

To adjust the strength post-print? Hrm. Maybe a shaped crafting recipe with one redstone dust, similar to how Gregtech chipsets are configured with a screwdriver? As an addition, though, I don't think it's a real balance/whatever issue to allow directly configuring blocks to emit weaker signals than the default.

It kind of is as other mods make semi-expensive blocks to do exactly that (including Microcontrollers).

Ehh, but those are dynamic. And potentially support bundled redstone. Here it's still just an on-off thing. One you could emulate with some redstone on the floor, anyway. I really don't think this comes close to anything worthy of comparison to MCUs? On the contrary, I kinda feel like making it configurable - any which way - makes it more powerful, even.

What would your suggestion be then? Have them be 0/15 by default, add redstone to increment/decrement value by one? Feels like it's over-complicating things a bit to me.

I actually like the gregtech way, just make sure NEI tells 😄

I do think it should require some extra resource, for example BuildCraft gates require the Comp Chipset (made with a redstone comparator) to be able to read/output specific redstone strength values. So how about crafting it with a comparator in a certain pattern?

But that would have to be a one-time cost. It makes no sense to consume one comparator each time you change the output (after it's been crafted with a comparator once). And no, I don't want an extra GUI for that. And I don't want to add extra book-keeping for that, to spit out a comparator when crafting if one was already used previously.

I second this. No GUI is always a good idea.You just need to find a clever way to add the comparator.

Hmm?

Actually, come to think of it... I'll just make it consume more material to print if it uses an output in [1,14]. Simple as that.

That's actually pretty clever.