I meant, that a person running this proxy node would also get the peer information from a node they are running simultaneously somewhere else, and the peers are collected organically via peer discovery. Then the proxy nodes can be gathered into some list online, and a load balancer can be placed in front of the various proxy nodes to distribute request traffic across proxy nodes, and hence, geographically distant full nodes. Only load balancer costs will be incurred in that case, while a rate limiter can be set to avoid being bombarded with requests and paying for too much bandwidth.
Historical transactions and blocks (assuming the proxy node impl can deduce the nodes running with -txindex using trial and error). But then again, it's much better than paying for an API token to fetch the equivalent data.
Also, trying to find a particular transaction or a particular block will be inefficient this way if you don't know which block you are looking for.
I know Electrum API is always a thing but that can't fetch blocks, and it can only get transaction history of an address you put inside your wallet. It's very cumbersome if you just want to analyze a group of transactions with different features (source address not being one of them).
If you are searching for transactions based on some criteria, and are making multiple queries, you will ultimately have to access the same block multiple times. The time it takes to query a block from a peer is going to be much longer than the time to query a block locally. So you will see negative performance issues if you don't have the blockchain stored on the machine (or accessible via storage bucket) running the queries.