Keep in mind that the DA 20-40mm f/2.8-4 was conceived along with the amazing advancements of recent DSLR designs. I've long had a K-200D and K-20D bought new but in a great closeout deal when the K-7 appeared. I enjoyed them for some years, but have moved on and should sell them, although they are still good cameras but with definite limitations. With the far better high-ISO performance capabilities of the K-5 series, f/4 became the new f/2.8, which was also reflected in a new line of f/4 lenses appearing in Canon's premium "L" category, being that similar advancements had taken place with their latest DSLRs.
Now with yet greater improvement in the K-70 and KP, a lens capable of good performance wide open at f/4 could outperform one of f/2.8 on your K-200D with ease. I love the DA 20-40mm f/2.8-4 Limited on my KP. I bought them in silver and they are classically beautiful as well. Now I only take my DA 21mm and DA 40mm Limiteds when I need to go extra-compact.
It is not that the K-200D cannot still take a good picture in decent lighting, but as you express in your own need, it limits what you can select among fine lenses that could work for you. So, if you are able and willing to move into the price range of such lenses, a body that will perform to take full advantage of what they offer, such as compactness with great imaging capabilities, is not stretching things. Also, visibly improved resolution, metering, and many other useful features have materialized. Then a future consideration might be directed for a faster Limited, such as the FA 77mm f/1.8, which is a favorite kit for me in a pocket along with the DA 20-40mm on the KP. Something to think about.
Last edited by mikesbike; 12-13-2017 at 12:46 PM.