SDKs and Beacon/Bluetooth LE development

There are a few beacon sites that released their SDK. For example, say https://www.gimbal.com/ has an SDK for you to implement in your mobile app so that you can talk to their manufactured beacons. Say you appreciated many of the features and tools that their software had, but you wanted to develop more tools... or maybe custom campaigns for their beacons to be programmed to do. How would you go about doing this? Can you build on top of an SDK? Mainly my question is, how can I program their beacons to do more than their CMS offers? If I wanted to build my own CMS with custom functionality and campaigns, could I do this? How would I go about doing this?

How does a Beacon works?
You have an UUID (which refers to a company), a major, an minor and a RSSI.
Let's try with an example. Let's say that the UUID is from BestBuy, it will be the same for all its BestBuy beacons.
Then, the Major will determine in which stores it is (the one in Atlanta, the one in New York, etc.)
Then, the minor will determine where in this store the Beacon it is (near the DVD stand, near the TV stand, etc.)
And the RSSI (with the Tx—1m information) will help you to determines the distance between the beacon and you.
But, since, an UUID is only a suite of hex values, major/minor/rssi numbers, you have to know what they mean (if its the store in Atlanta or the one in New York, etc.)
So it means that the app needs the knowledge, inside it, or by asking a server
So, as long as you're connected to this database, you're good.
So I don't know about their SDK, since I worked with a custom made iBeacon, but it means, that if the SDK allows you to access the "numbers" and not "the translation", you're good and can do whatever you like. It depends on how much "transparency" the SDK give.
In other words, you could provide an "complement" of the SDK with your own.