I know this is a tad late but my 2 cents since I just got back around to EthereumJ.. Just some ideas for people who may stumble on this..
Java has a webview client built in, https://docs.oracle.com/javase/8/javafx/api/javafx/scene/web/WebView.html.
You could then run an ethereum node on each client and host the HTML on the server.
This would be the best use of the blockchain. You could tell the nodes to look for the blockchain data at the server IP as well if you wanted to edit the core, but then you lose consensus.
You could run a full node on the server and your lite nodes could interact through one of the many libraries that use http.
Here's a project I found using webview to browse the ethereumJ blockchain https://github.com/Bitcoinzie/EthChainExplorer
I doubt it still works as it's a pretty old repo, but it shows how to accomplish what your asking.