Use pumps to pump water and magma to the top of the map (build a tower of up/down staircases and two separate rooms spanning half the map, pump water and magma up then stop pumps and let gravity drip them down over the pipe), then use it to make a raw obsidian tower to the top of the map over the magma pipe. Carve it out and move ALL living facilites into it. Bonus points if you make some magma lakes because honestly there's never a situation where you can have too much magma. Engrave the entire thing too just for style.
Actually, if you wanted you could theoretically create a completely internally self sustained biodome of a fortress in a water/magma cast obsidian tower because it counts as natural rock and can be muddied for irrigation/tower caps. I'd make the barracks and the trade depot at the entry level, personally because I'm lazy I'd channel out around the magma pipe itself and start my tower's foundations underground so I wouldn't need to bother with pumping magma up the tower for metalworking. I'd also keep the farms on a lower level for easier irrigation. Tower cap farm could make up a few levels, probably above or below the normal farms. You'd still have to tunnel around for minerals.
If you want to get the chasm involved, after you've built the obsidian tower and have moved in, shift focus to clearing out the chasm, then build a floor on the bottom level and use scaffolds to engrave THE ENTIRE THING. Put expensive statues and other works of art throughout the place.
Could make for an interesting fort if you've got some bauxite for the pumps and the patience to build a megaconstruction in order to build another megaconstruction.