Dear Daniel,
while you're on bundle operations for ECL, prologue-code and epilogue-code must be removed from the operation (and thus from make-build) and moved to the system definition (where it is already accepted since ASDF 3 pre-releases).
ASDF does NOT properly handle operations with initargs, and is unlikely to without major refactoring, potentially incompatible changes, size increase and slow down.
—♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics• http://fare.tunes.org If you could ask a unique question to a computer during a Turing test, what would you ask? — Douglas Hofstadter, Metamagical Themas