I believe this is an area few have explored, and it's really too bad. Using custom content properly gives you an edge over others as you can control with a great deal of precision the on page seo factors such as keyword density and readability. 

From this we learn first that search engines basically ignore stop words. So, when building custom content, we only need to focus on the actual core of the content, not so much the little details. 

Now, to make this work, you need to do serious split testing. For those that have never done split testing, it's really quite simple. You will want to setup several groups of domains, all using the same keywords. Lets start with 5 domains per group and start with 5 groups. This gives us a total of 25 domains all using the same keywords. Keep everything else the same as well such as template, linking, etc. This way we narrow it down to only content as the deciding factor. Now, for each of the 5 groups, find a base article to use for your custom content. Something related to the niche would be good. Now, we go through and perform our replacements. In each group, we vary the keyword density. In a couple groups you may even consider adding small amounts of scraped content. Just a few sentences for example. Here is a run down on custom content :

Custom Content

Straight from the page:

You may provide any type of content you wish here. It will be treated as an extra source for every domain using this settings profile. Keep in mind that the specified content filters and settings still apply. 
The beauty of this content source is the ability to specify optional terms to use. You can do this by clicking on the icon below to add a group of words or phrases to your content selection where you cursor is currently placed. 

So lets, throw out some ideas for usage, and show some examples. 

The First would be the potential for use as filler text. Lets say we have a domain group setup for all of your “red widget” affiliate domains. You can find some “red widget” articles, paste them in the input box and the system will then mix that content in with the scraped or rss content per your settings specified earlier. This can help create more readable content, and ensure that none of your long tail keyword pages are ever blank because of a lack of content. 

Lets look beyond the basics though and dive into more advanced usage.

Well, this input box also allows you to insert the keyword token, so now you have a way to control on page keyword density by sprinkling your keyword token throughout the pasted article at specific intervals. This is a great way to raise or lower the overall keyword density of your generated pages, but it isn't where we stopped.

We've gone a HUGE step further by creating a system here where you can completely build human readable content that is 100 percent unique quickly and easily. If your pages don't have awesome content on them it is now no ones fault but your own. So how do we go about this?

Pipes.... By using pipes we can build a group of sentences that have hundreds or thousands of possible structures and outcomes without much effort. Lets create an example and see what I am talking about.

Lets start by typing the following sentence into the custom content box: The boy ran to the store.

Nothing exciting there, but wait. Highlight the word boy, then click on the gear with a plus sign that says (Click to customize content). Now you will be prompted for words to replace “boy” one at a time. Enter buy then click ok, enter dog, then click ok, enter cat, then click ok, lets stop there and click cancel on the next box. You will now notice that your content looks like this: The {* boy | dog | cat *} ran to the store.

When a page is generated we now have three possible sentences from this single sentence. It can be:

The boy ran to the store.
The dog ran to the store.
The cat ran to the store.

Lets go further and change a couple more words: The {* boy | dog | cat *} {* ran | walked | drove *} to the {* movies | store | market *}.

Notice that I replaced all but the stop words in this text. Search engines ignore stop words when indexing pages so they can focus on the core of the content. So what does the above quick sentence yield as far as content? We now have the following outcomes from this single sentence:

The boy ran to the movies
The boy ran to the store
The boy ran to the market
The boy walked to the movies
The boy walked to the store
The boy walked to the market
The boy drove to the movies
The boy drove to the store
The boy drove to the market
The dog ran to the movies
The dog ran to the store
The dog ran to the market
The dog walked to the movies
The dog walked to the store
The dog walked to the market
The dog drove to the movies
The dog drove to the store
The dog drove to the market
The cat ran to the movies
The cat ran to the store
The cat ran to the market
The cat walked to the movies
The cat walked to the store
The cat walked to the market
The cat drove to the movies
The cat drove to the store
The cat drove to the market

That's 27 completely unique sentences generated from one sentence and 3 word changes. Imagine the possibilities if you create a dozen variations for each word and you do this for a 30 sentence article instead of a single sentence. You can create thousands of unique sentences for hundreds of keywords. How would I use this? Lets say we are doing a group of 5 domains related to the mortgage industry. I would go to google, search for “mortgage articles”, then copy and paste a good one into the custom content box. I would then go through and create variations for every non stop word in the article. (stop words are words like the, and, a, an, because, to). I would then place my keyword token in the sentences in places where it makes sense to have it. This gives you control over the keyword density and overall readability of your content. In my opinion this is one of the most powerful features of the new SSEC version. If you are getting banned after this it isn't because of content. You can also mix this stuff in with scraped content, rss feeds, or use this solely as your content source.
The same system is available to you in BC as well, so this applies to all of our software. 

Now, sit back and watch these 25 domains carefully. Find out which domains 

1) last the longest
2) Provide the most traffic over the course of their lives

Once you have a working formula that you can repeat, you have a golden ticket. You will then have a recipe for good content that doesn't get banned, provides a good ROI, and that is unique to you. 

On a side note, watch other factors that lead to bannings. I personally have stopped interlinking my domains. A small pool of ip's all linking to one another certainly sets off red flags. It worked fine a couple years ago, but things change and we all need to evolve. This is where Link Exchange comes in. The ip pool and server list is quite large, so you end up with a very diverse pool of links . Build links slowly, make your sites appear WH, but most of all, do what gets you the best ROI. This is just one method you can try.