I recommend you ask your question at
http://nuclearphynance.com/. 95% of the people here are those who never made a full-time career in finance, hence you will invariably get a lot of stupid advice from those who claim to understand the industry but who do not.
I worked on the exotics rates side before. Depending whether you express interest in a) flow products or b) the less liquid "exotics" the required skill set is very different. When I say flow products I mean caps/floors/swaptions/CMS/... because those are part of the exotics rates group at most ibanks.
a) quantitative mind set, firm understanding of probabilities and statistics, fast number cruncher, people skills and sales negotiation skills. Most likely you spend more time talking to interbank dealers and your sales force than crunching numbers. But you still need to have a firm grasp at how to re-calibrate vol surfaces/cubes.
b) heavily reliant on mathematical and statistical concepts. Advanced knowledge (meaning at minimum good advanced Master's or Phd degree) of mathematics, especially measure theory, stochastic calculus. But also advanced knowledge of probabilities and statistics. Programming skills come secondary but are still important to have as most of your applicant peers most likely know C++, Python,...
The position you mentioned can definitely be a stepping stone, I have seen people transition onto the front office multiple times. All you need is the required skill set (as detailed above) and a keen willingness to learn and curiosity for the products and market. What works IMHO the best is an honest approach such as admitting you don't know much about how such products are traded and hence ask a trader to spare some of his time after hours to walk you through in exchange for you wanting to make his life easier via project or programming work on the side. That is much better than being pretentious with a big mouth but getting exposed as a know-nothing.
Hope this helps...good luck...