2) Even very casual users of some very minor drugs risks the eventual progression into Burnout stages
No they don't. Not if they simply not use every now and then. It would take AGES for some Drugs to ever become a problem. If you drink Soykaf ALL the time, you'd be rolling once every 10 weeks. Let's assume Soykaf is Psysiological, so Body+Willpower to resist, that's 6 dice for normal people. 2/3 chance to succeed, so once every 30 weeks you'd fail. So you'd have to be dosing on Soykaf for 2.5 years average in a row without ever taking a break to start hitting Burnout. If you're a runner with decent stats, it's 90%, so 100 weeks per failed test. That's 8 years average of constant Soykaf drinking before Burnout. That's CONSTANT use. Casual users have only very small risk of ever hitting an addiction level, nevermind all.
The fact that with average rolls, someone will hit a coma in 8 years of 1 soykaf per week is outrageous. There are people who have lived decades, drinking the real world coffee equivalent once or twice per day, and never advanced past mild addiction at worst. And again, this system does nothing to differentiate between someone who uses Kamikaze once per week, or once per day, or once per hour.
Besides, you're ignoring a VERY important aspect: The drugs are supposed to be risky, because if you don't have the risk from continued usage, everyone would be doing it. There's a system requirement that there's an actual risk involved even for casual users.
Also, buying hits on a crucial roll? Not cool.
I am not ignoring their risk. With the system I came up with, the person who drinks 1 soykaf per week doesn't have to worry about Burnout, unless both the GM and Player feel that they want to add that complication to their game for Soykaf. Then, the risk is there.
What I came up with also differentiates between the 1 kamikaze per week, and 1 kamikaze per day user, because multiple uses in a set time period make it harder and harder to resist addiction. Basically, I have a time period based on Addiction Rating, and each additional use within that time period adds +1 die to the opposed roll. Skipped time still drops it, like it says.. but with mine, Kamikaze rolls 3d6 vs your resistance roll. Each additional use in the time period, gives it an extra die. So, someone who uses once is rolling vs 3d6, while someone who uses 7 times is rolling vs 9d6. Frequent use penalizes, and adds risk. It doesn't ignore the risk. In fact, I could probably tweak it to keep the threshold, and just increase it for multiple uses within the time frame I came up with, for those that want to keep the threshold.
And as for Crucial Rolls, the GM doesn't have to allow Bought Hits, I just have that because I would likely use Bought Hits to simplify for the person who buys 1 soykaf per week.. your average person can buy 1 more hit than the opposition.. until the Soykaf user starts to binge, at which point I would call for a roll instead.
I think I will post my writeup in the House rules section, for perusal.
