I think I understand what you are getting at but I don't quite agree. The parser functions are more like function calls. In that sense, I don't see how it is much different than using Lua; which, by the way, still has to use a parser function to invoke the script.
Lua requires quite a bit of extra infrastructure inside the script to do similar things. It's great for more complex things, but Prev/Next might be in the gray area of Lua being the better choice. Does anyone know if someone already wrote some Lua to do a similar thing? It's much easier to copy/modify than write it from scratch.
Also, you have to make a template to invoke the Lua module, so it seems like more trouble than it's worth. However, if the OP decides to go the Lua route, it would be an excellent learning experience and something that could be repurposed and expanded more easily.