Several things to keep in mind about the Nestle setup. They appear to treat it differently on different Nestle sites, but in general the setup is such that...
a) the link to the each of the other brands is at the bottom of a fairly long drill-down chain, and is only one of a bunch of links on the linking page. The others are nav links back to the main site.
b) the anchor text is never a keyword... it's always the brand name or the canonical url for the domain.
As such, there's little PageRank loss, and also very little linking credit conferred. This is unlikely to be seen by Google as a linking scheme. And these are all established brands.
This is in contrast to the example suggested...
...like having a site called "Health" and then having individual sites dedicated to asthma, foot pain, heart attack etc...
I think there's a huge
difference, not to be minimized in this discussion. It used to be said, when blogrolls were the linking scheme du jour
but it was clear that Google was catching on, that Google would let you get away with it as long as you stayed with the site name and didn't try for any keyword anchor text. There is an analogous consideration here... those blogroll site names were brands.
...about 200 more domains which are specific in a similar way to the 80 and would like to link those from Top as well
Candidly, this sounds like a linking scheme, at least to me. I think the issue of whether they look bought is a red herring. The greater issue is whether this looks like a natural situation... ie, whether these are real companies, or just keyword domains. Sounds to me like microsites in reverse.
You are quite correct Jim that these sorts of things should not be hit quickly. if it takes a couple of months to roll everything out, so much the better.
A couple of months? No way are these going to be remotely seen to resemble brands in a couple of months, not even in accelerated web time. Again, personal opinion.