Ok heres my idea on pipes: Pipes could be 2 pixels wide and would be as long as you pick to be made from a 1 tile pipe to a 10 tile pipe, there could also be different widths for more amounts of water but if too wide dwarves can't pass through the tile.
The different types you could get would be: horizontal T junctions, horizontal corners, vertical corners, vertical T junctions, straight horizontal, straight vertical.
You could also add more complex things such as pumps, which would increase the pressure/ speed at which the fluid travel through the pipes, pumps would have differnet settings: weak, medium and strong, these would require different amounts of power, valves, these are like normal pipes but when off don't let fluid through, toilets, which you add a pipe carrying water to the input tile and sewage comes out the output tile, baths , pretty much the same but sewage doesnt come out and is used or cleanng dwarves, fountain same but are for decoration although occasionally a drunk dwarf might jump in,taps , where dwarves may fill buckets, drinking fountains where dwarves may drink, water shooters, these can shoot water and the distants and power depends on the pressure/speed of fluid coming through pipe, these can also be aimed at different angles to get different heights, and finaly fonts where dwarves can be baptised.
Of course magma could only be put through magma safe pipes and pumps ect. Pipes maybe attached attached straight to the output of screw pumps. And low quality pieces could leak, like if there is a pump pumping up 3 Z-levels to the leak it wouldn't spill very much but if it leads to your super high pressure water shooter then you might have a problem, especially in magma transportation / sewage disposal systems as spilling sewage everywhere makes dwarves sad.
The 3 new fluids I am requesting are : sewage , blood , and beer/ale.
This would be so fun I mean imagine using blood to squirt goblins into your pit filled with spikes which drains of inot your blood tank, oh the irony! Or pulling a lever and a nobles bath fills with sewage or even magma! And of course what church of Armok would be complete without fountains of blood and dwarves being baptised in blood, or at a party you pull a lever and beer/ale comes out of the taps, fountains and drinking fountains or you could be evil and make your dwarves drink sewage. And mad dwarves / darves in cults would drink blood.
Also please could you add an option to anything linkable to levers or pressure plates to default to on and dwarve cannabilism as when too many immigrants come they take to much food so my dwarves starve and I want my dwarves to eat other dead dwarves if they are really hungry or if they don't know its dwarf meat.