If we did, I say that we should strive for something vastly different, both in gameplay and visuals, from the start. Don't want to let someone accidentally believe that we are imitating their game like what happened with dwarfed...
Underground moss farming, tower caps, have to dig out surrounding space, smoothed floors don't hurt but have growth penalties, engravings give a happy thought bonus when rested on, overwork leads to madness without sufficient time for happy thoughts, madness leads to jail time(with a standard "time passes" prompt, but over in an instant), too many and you risk death, but making an artifact will negate one jailing... Above ground you can find actual trees, and plants, but unhappy thoughts and no moss/ore, neglected floors eventually "cave in", becoming rock again. Toss in some unrealism that benefits gameplay with growing gems in rock, some gems only to harvest, others because they cause passive bonuses to nearby floors, then expand that into certain gems cause the growth of special, though mostly worthless mosses, and you have a crude imitation of alchemy at a macro level... Maybe you can still use your poo, but only to fertilize mushrooms and above-ground stuff... Cultivating certain gems to boost the chance of certain ores coming from that floor when it next caves in... A gem will morph into the next level if given sufficient quantities of it's produced ore...
Of course, the real challenge would be keeping it unique. So, I reccomend that a tool's quality would affect the quality of produced objects, walking is a free action (available anytime, though enhanced by wearing appropriate shoes)... Needs traps, to keep intruders out. Player hit with trap loses sanity and flees to surface, if the trap is more powerful to overcome random chance and their armour bonus. Time to be kept in dwarven standard, of #cats produced in one day by a single mother cat to replace the second, number of seconds before a kitten grows up to the hour, and minutes placed in the middle to give the same number of minutes in an hour as seconds in a minute
By donating money, you can purchase the seeds and resources that can produce the products otherwise only available to purchase from elf caravans...
However, that is just a rambling parody, so if you really are serious, try to make something unique, and not just shoving toadwater and DF together in a way that compliments neither and infringes heavily on both like those paragraphs above do.