What is exactly your concern about "scaling", what do you feel is not scalable, can you elaborate ?
"Scale" in what sense ? Technical ? Or economical ?
If the former, I would need you to clarify your concern because I don't see what is the scalability issue you are concerned about.
If the latter, I think the "bidbot investment" does not NEED to scale - this is what I was referring to when talking about diversification. The "bidbot investment" will stabilize to an equilibrium level that will be reached through market mechanics.
As an illustration, the early bidbots (booster for instance) were distributing 80 - 85% of the bids. Some people saw the opportunity and started offering bidbots that pledged to return 100% of the value of the bids (the rising).
Then even more aggressive offers appeared, such as spydo and tipu which also return (under different form) a part of the curation rewards.
For as long as there is demand for bidbot services, and that demand outstrips supply, there will be people ready to offer those services. If running a bidbot becomes more expensive than the earnings, the operators will need to reduce the payout to investors. If on the other hand the people buying bidbot services would feel that they don't provide enough value for the risk, they will reduce the sums used for bidding (potentially down to zero)
It's a free market (for attention) at work, and it works pretty well.
However, it is fragile - it depends on the aggregate number of eyeballs which the content can reach. This is why steem needs a wider array of services on offer, thus allowing investors to redirect their "steem power" capital to the most profitable opportunity.