Yes that would work. Also, do not think that just because you build a 2nd link from same source its value is low. I would say you can easily build 10-20 links from same source without a significant decrease in value. After 100 links you would obviously get less and less value from each additional link. Also it matters a lot if the links have same anchor and point to same page or not. 20 links in-text (as oppose to sidebar, footer, etc), pointing to 20 different pages and using 20 different k-words would be a lot more valuable than 20 links pointing to same page and using same k-word.
Also, I would recommend building the links from different pages of that source site. In case that wasn't obvious.
Now, going to the reusing the sources for your web2.0 properties and support sites, that is perfectly ok. It is not a "flaw" as you call it. It's just that our devious BH minds can find stuff like this and use it to our advantage. I would not recommend doing "100% coverage" as in that case you might be able to be detected as doing a link scheme. I am not sure about this, I'm not even sure if it is practical for Google to do this kind of analysis but I prefer to stay on the safe side.
Bottom line is I do manual commenting on DF sites for example. I try to find high PR, trusted sites that accept dofollo links in comments. Obviously those are not so many so I reuse them a lot. Good thing is they are usually super large sites (1mil+ indexed pages). That means I am not obvious. Also, it is easy for me to blast some links at those source pages to increase their PR even more than it would get naturally.
In the end, you just do this stuff for let's say 4-5 self-hosted sites and 50 web 2.0 properties and you rank pretty well.
However there is more to it than just that. If you're targeting more difficult k-words you also need a good IP diversity. For that an AMR blast, posting on forums (preferably related forums or threads) and any kind of link that adds a new referring IP to the list is a great idea. Now don't get me wrong, these days AMR blasts and these kind of links are quite crappy. However, because they increase your IP spread and are combined with more powerful, authoritative links, they help a lot overall. You don't take just one link, look at it and say it sucks. You take the whole link profile/strategy/structure/whatever and analyze it as a whole. You need the following types of links to succeed:
- Relevant
- From trusted sources
- From many IPs, A,B,C-classes, datacenters, domains
- Of different types (in text, in sidebar, comment author, in comment body, in forum post) - this helps with looking natural more than ranking well
- Using different anchors (k-word, generic word like 'read more', URL, etc) - this helps with looking natural too
Generally you can't get all those things with a single link. One link will be less relevant but from a trusted site, other link will be very relevant but from a weak site, etc. You combine and you succeed. The only thing you have to do is actually DOING IT! So many people complain that SEO is hard, that they fail, etc. They don't really work. They don't do the boring manual work required. They are lazy. Unless you are targeting a really difficult k-word, ranking is not that hard. For example you could get a MNS ranked with just a bunch of manual dofollwo comments. I ranked some MNS on #1 with just 20-30 df comments and 10 forum links or so. Those MNS don't make a lot of money but they do make more than I invested in them and all the MNS togheter over a longer time make quite a nice amount of money.
