I am by no means a lung cancer expert, but currently there is contention about whether lung cancer screening in smokers is worthwhile, and I doubt at 6 monthly intervals. Some studies have shown benefits from screening for smokers, but I dont think any high quality evidence exist which shows a clear benefit of screening. There are options for screening, chest xray, CT chest. A CT chest is more sensitive than a chest xray but doing it every 6 months is going to cause much more harm than good.
My more general point is that these are recommendations which need to be evidence based, and doing more harm than good through false positives, excess radiation exposure, etc is a real risk. I dont think its helpful to make suggestions that are not based on evidence.