I don't think I would be a good match for bank culture or HFT, but if the work you describe is in a small-to-medium sized asset manager or hedge fund, then I would not mind, and would find it enjoyable. I worked at such a place a number of years ago and it was one of the better jobs I've had.
The trouble I find is that a lot of small-to-medium sized asset managers and hedge funds don't have very good technology practices in general, and are pretty far from sophisticated use of low-level Python. There are often a lot of political reasons why they cling to Excel/VBA, R, or MATLAB, and there's almost always some political battle happening between the people that want to rationalize the system to a proper software design, and people who just want to keep cranking on the hodge podge of existing tools.
I'd probably be fine with some trade-off regarding all of that, if the pay was acceptable and there was a strong commitment to a healthy work/life balance. But among finance firms this is extremely hard to find.
So even though I am not at all opposed to doing this work in finance, I still find the volume of acceptable job openings in that field to be too small to make it realistic.
Since you really want to write C and Python... Do you care if you have to write trading code to help billionaires make more money?