A brand is ultimately a promise. It says "if you buy something from this brand, you will get services X, Y and Z"
There will need to be clear differentiation of product if the different brands are going to have any value. You can see an example of this in the large hotel chains - some of them will have 10+ different brands, all at different budgets but each deliver a different product from the cheep'n'cheerful to the ultra-luxurious. An example is Accor which ranges from their Raffles brand (yes, the Singapore hotel is part of the chain) down to the Ibis Budget chain
If you take a bad product and give it a new brand, it works for a while and then eventually customers realise that it's still the same old product