Yes. I wanted an SLC 300 but without the AMG Line extras so that I could add the ones I really wanted. Mercedes marketing in the UK doesn't allow customers that choice! I bought a new 200 Sport automatic at a big discount and added my own choice of extras, then looked at tuning it.
I tried to find out whether the 200 and 300 engines are absolutely identical (I believe that they are) and whether the turbocharger and intercooler are the same, but I couldn't get an answer anywhere. If the hardware is identical then a remap to the 300 version should be possible. Why Mercedes didn't increase the power of the base model when they introduced the bigger, more modern 2-litre engine is beyond me.
In the end I talked to a reputable company that offered a 50 bhp increase, with a similar torque rise, using their dyno to set it up. It works well, around 6.0 seconds to 60mph and no adverse effects at all.
Send me a private email if you want more details.