>giving us REPL to interact with the application during trading session
This to me is what the big appeal of Common Lisp for a trading system could be, particularly if it allowed live recovery from errors (dropping somebody into the debugger, rather than just core-dumping), which could save a lot of money by reducing downtime. But as you say it would require redoing everything to make the code fit latency constraints and be cache friendly, which would be a lot of work.
This to me is what the big appeal of Common Lisp for a trading system could be, particularly if it allowed live recovery from errors (dropping somebody into the debugger, rather than just core-dumping), which could save a lot of money by reducing downtime. But as you say it would require redoing everything to make the code fit latency constraints and be cache friendly, which would be a lot of work.