We want to launch a baker node. Can we use only one URL with a link to several nodes for baker, endorser, accuser? I mean so that one baker is launched and it is communicating to 2-5 nodes via one point of failure?
There are no URL's involved in running a tezos node. You can run a node anywhere and it will connect to the P2P network. You can put your node in private mode, which means that other nodes will not include your node in their broadcast lists.
Some bakers run a setup where they have several "public" nodes, and 1 "private" node which only connects to their own public nodes. (This is overkill and unnecessary as it does not provide any additional security).
The tezos-baker binary requires a node be running on the same server. This could be your private node, connecting to each of your public nodes. You can run node/baker/endorser all on the same server.
The baker cannot communicate to more than one node at a time as it requires a local node on disk.