2. I agree with you comment that it is easier to think about concurrency in Haskell than in something like C++, however you can't really compete with C/C++ in Haskell. Not even with cgo (Go packages that call C code), not with OCaml or any other higher level beasts that promise the speed. Fortran would be the only one faster for the "algo" part of your initiative. But again, if this is just an exercise, Haskell and others (I prefer Clojure for example :) will do just fine.
3. Would make sense to split the "platform" in two (very different) parts: "Quantitative Analysis" (a collection of tools and rules) and "Technical Glue to Read and Stream". Each can/should be divided further of course, but the two above are essential yet very different for a true "HTF Platform".