I really enjoy the base building and design aspects of this game. Over the course of the last few years, I have been thrilled at the advancements made in this direction (notably terraforming, stockpiling, auto-paving a selected area, and stacks), but one avenue that continues to give me grief is metal paving. I think laying metal looks really neat in this game, but I feel that the resource cost to make a pavement of any significant size is too high. The issue as I see it comes from two sources: first, the difficulty of obtaining metal in large quantities, and second, the necessity of using metal elsewhere.
Take stone or brick for example. If you give me an hour, I can generate enough brick or stone to pave an 25x25 area, which I think is a suitable time-frame to make an area more aesthetically appealing. I want to note that 25x25, while sizeable, is typically a fraction of area for most villages that manage to reach all aspects of industry in this game. Sure, brick requires clay, fueling a kiln, and waiting for the clay to bake, but the process is low risk, takes a quarter of the time that ore takes to smelt, and it's very easy to generate hundreds of bricks even with just two kilns.
Compare this to metal: You have to find the ore, you have to brave the mines to reach it, expend tons of energy and time extracting it, throw it in the smelters and fuel it up, and wait 45-60 minutes, often to only receive a few metal bars. The issue is further complicated by the fact that metal is used in so many important recipes, ranging from curios to weapons. I really enjoy the satisfaction I receive from going through the process of obtaining and refining metals, but I don't feel this translates to the aesthetic portion of the game.
A few worlds back, I decided to give metal paving a shot, and I paved a 20x20 area with bronze. The entire project took me over a week to complete with four smelters, and though I could have probably truncated the time by building another 6-8 smelters, I didn't really want to dedicate such a huge portion of my base to the same structure over and over, especially since it would end up being useless after I finished laying the metal. If I had decided to go that route, I surely would have ended up destroying the smelters at the end of my project. I didn't keep a record, but I probably mined 2000-3000 ore to pave this area, and the end result kind of just left me feeling guilty about using 400 bronze bars for aesthetic purposes when I could have been making armor, curios, whatever. I can't imagine using iron to pave instead, let alone wrought, steel, or precious metals.
My suggestion is to change the paving requirement for metal from bars to nuggets. I think this significantly lowers the threshold of difficulty of obtaining a large quantity of resources and greatly opens up the potential for beautifying an area. I don't believe this will result in insane activity like a 100x100 area of gold until perhaps the very late game, and at that point, I almost think a celebration of decadence is in order. I absolutely love the idea of a brick road lined with gold, but I cannot fathom a circumstance where this is possible without an incredible amount of manpower and time. Please consider reducing the cost to lay metal, it has so much potential to make some very unique looking bases, and I just don't feel this option is accessible without the use of scripts or bots to automate the process.