Launching a full-fledged paid product is even harder, I guess you'll need to secure at least 3~40 headcounts just to integrate this into many subsystems inside Google. And this needs some senior executives driving the project since this is a cross-organization project between research and products. This creates a structural problem, in that they usually expect bigger impacts from these kind of projects to justify the cost. It's possible to pursue without involving top-down decision makers, but usually that kinds of project tends to fail to create consensus since everyone has different priority.
So "a separate small, experimental product" is not going to work unless 1. the model becomes fully productionized, generally available inside the company so a single VP (or even director) can quickly build a prototype to demonstrate or 2. someone successfully proposes a convincing path to the major billion user product to draw senior executive's attention or 3. the research team decides to build their own product team from scratch and aggressively invest into the sub team.
I think Pathways is one approach to tackle this issue at scale by making the network sparsely activated so the computation cost can be somehow bounded based on difficulty of each query. This effectively gives Google knobs for the axis across computational cost and the result quality by limiting the size of network to be activated. If it turns out to work well, then we might be able to see it incorporated to Search in a foreseeable future.