the other answer is flatly incorrect.
the valves are a very common problem and known on this engine. the other answer provided was a generic answer that could apply to any car that is smoking. a 650 that smokes after idling is a valve seal propblem, period.
yes, my advice is to get the valves done (fix it) or to consider trading it if you dont want to make that kind of investment (which you initially indicated you did not want to). if you prefer to get a replacement engine rather than a valve job then that is essentially equivilent to fixing
if you review your original post, you asked what the alternatives were. there are only two alternatives - fix the valve seals (either by having them replaced or replacing the engine) or trading the car. there is no alternative where this issue is resolved otherwise.
this car can be hugely expensive to own over 100k, and I was sharing this with you a friendly gesture. If you did not want this advice then please disregard. Usually customers like to have more information than less, which is why I offered this info to you.
please let me know if you have further questions.
Please do not forget to CLICK ON a positive rating on my answer so that I receive proper credit for my time and correct answer.