Before anyone else says so... yes, I think I've seen (and, for some, participated in) suggestions for each of these, before...
Not to say we can't still talk about them, but I'm sure
someone will be along to point out all the prior threads.
Personally, I fancy the idea of the Paternoster lift/elevator system. Entire "raising/lowering" rooms would be interesting, but might be more difficult than a single (or dual, side-by-side) tile system which is set up much like either wells or vertical axles.
My own ideas about conveyor belts include needing two bins, for every length, one for input, one for output. You can only put a given amount of items in the input bin (defined as per stockpiles), operation will skim one item (or perhaps multiple, if small items with a low actual size) from the input bin and move it on a tile's worth of space, but only as long as the next tile is free. The last tile of the belt will only drop the item into the output bin if the bin is not full, otherwise it stays where it is, and clogs up the line for all other items. Optionally, the end of a belt (whether you use a bin or not) can be placed to land onto another belt. Either the end (so making a belt longer than the 10-or-so-tiles I envisage a single conveyor-construction would be at maximum) or part way down a perpendicular one (so as to make multiple branches feed into one main system). Again, clogging up would advance back along the belt.
Steam-based devices does rather depend on a different tech-level from what is currently given to the DF world, although there has been Official mutterings about pipes allowing water to go through magma tiles, or magma to go through water tiles. Whether that would even end up as creating steam that
itself can be piped to appropriate users of this energy, I don't know.
Pivoting has certain problems. It can only really be 90-degree pivots, instantaneously. And either "only when there's no blockage' or in similarly atom-smashing form to unraised bridges (which, incidentally, don't have any accurate "vertical" footprint to match their horizontal one... I sort of imagine them as being convertinaed back into the single-tile-height wall that they become...) Not that I haven't thought about things that can be done with this, of course.