How about this... Keyword/Secondkeyword.com eg. buyrealestateinvesting.com buy real estate(kw1)real estate investing(kw2) effectively reaching to keywords in one DN of course this is an example and is assumes search engines care about DNs which i think they do.
I thought the same thing when I reg'd BuyDomainNamesForSale.com It contains both (Buy Domain Names) and (Domain Names for Sale) also you could say it has 3 and consider (DomainNames) one. I've gotton mixed responses from people. Some like its keywordyness. But most dislike the length.. Although it's pretty easy to remember a straight forward phrase such as the above. those are my experiences.. Cheers.