Recommending the addition of some sort of exponential state enhancer that would provide one time 1% increase to a stat upon consumption. These could be found as a super rare item in high level expeditions or through special events. 

My rationale for this is that as players reach "end game", the stat growth becomes rather linear and limited based on drug/alcohol cool down timers, which is relatively easy to max out at current market prices.  By adding in percentage based growth enhancers, it would provide incentive to spend high amounts of in game currency on these rare items for high level players. 

No; awful idea. Torn is predacated on that, the lower end players will never touch the top end ever. And you could argue the same right now, but the rate by which you gain stats varies, but it's generally consistent at the higher end of the stat pool. 

I will use SATIRE_RELOAD, as an example; his stat loss is a nice consistant rate; it's 20/ just over 20m per day. So he has been away from the game for 10 days, guy has lost 200m stats in 10 days (it';s more but we can point to 20m per day just for refernce sake), now suppose somebody would be able to buy stat enhancer's at the classic Torn rate and players spent the money. 40m stats per day assuming it's done the same as Torn, it would be so drastic a change. And yes, players out there are stocked and ready to go; waiting for that golden goose of an update. Hoarding vast wealth. 

As for making it a rare/special event item. It goes back on what you already said, imo. You'd have to wait the year, to get what the top en dof players are after; more stats etc. You haven't really addressed the issue, being that your getting bored with the consistant rates and alcohol use. It's still gonna be locked behind an event and so it isn't even necessarily ideal for gym gains? if it's a one time per year thing. 

It will just widen the gap; and we will be playing another version of Torn within the next couple years. From a player to player perspective.