If your looking at developing a website then I'd say go for a brand/keyword mix of your own, its really not hard to do, keep them short and simple, but I would steer well away from the bigger brand names such as Ladbrokes, unless of course you get written permission from them, but that is effectively like leasing the domain rather than owning it. As the Ladbrokes name is patented then you wont be able to sell it on because you will be profiting from their name.
I think many companies would be okay with it but only if you advertise their own brand, so if you own a Ladbrokes based domain and have some rotating banners further down your page promoting William Hill, Paddy Power, etc, then it could land you in hot water. Some people dont think about it, but if they put up some Adsense text/image ads (say absent-mindedly) then they are effectively sending traffic to websites other than Ladbrokes.
There is a reason many companies dont like affiliates bidding on their brand name in PPC advertising, simply because the people looking for them are probably going there with the intent of buying from them already... so it is brand loyalty at its best, so in the merchants eyes its sort of like stealing traffic from them because those keyword conversions will be higher than normal traffic.
Also, when it comes to it, you may want to sell a domain + website down the line, you would generate far more interest if the branded domain was your own. It will be much harder to shift an already branded domain I would think.
In my opinion, if you do decide to go that way, then do it with the intent of promoting only the brand in the domain and get permission from the merchant first. Tell them of your marketing plan (not just SEO for their brand name) and if you are going to do some PPC or SEO for keywords away from their brand then they may be more understanding.
You can generally tell which merchants dont like their brand being misused by simply looking for them in the GKT, an example is Epson, type Epson into the GKT and see what results it generates with the brand name Epson in them, then type in something like Panasonic. Many merchants frown upon it, some more so than others, so it probably just isn't worth the aggravation.
Terry (WiganWebs)