If you make all options available to all classes, but give certain classes a "discount" on acquiring certain options, you'll keep the class system, but increase flexibility.
So, basically, Rolemaster. I still don't like it. Class systems have their limitations, but there are things they do really well, and once of those things is holding the gate against fiddling. To put it bluntly, no point based system is going to tell you what a monstrosity you've created when you've got a rogue variant who traded in a couple of skill points to get the ability to cast invisibility. As the ninja and spellthief demonstrate, it is a necessity to keep sneak attack dice and opportunities to use them in proportion to each other. If the spellthief had full sneak attack progression, then skill points and evasion or no, there would be few rogues left in the world.
As far as the "rumormonger" class goes... for it to be a reasonable choice, it would have to have something to do in an adventurous situation, whether that's intrigue at court or delving ancient tombs. It is not enough for a character to simply be good at something. The party is counting on each character being good, in general, not just good at a particular thing. A rumormonger is going to end up sitting on his hands a good deal of the time, and focuses primarily on activities (research and talking) that are frequently boring if played out. To get the class to even have a meaningful tactical level to play on, you would need advanced rules for contacts, intrigue, and information gathering. You'd also want to move to a variant XP system. Although it's hard to imagine how much XP such a character is going to earn the in context of walking around talking to people and looking stuff up. The only way for such a character to be interesting, to me, is for them to experience personal drama, which is far outside what D&D is intended to do. Seeing your village incincerated by a dragon, and being unable to do anything about it, escaping with your scrolls and reflecting on how paltry they are compared to human life, well that could be interesting, but it's not worth any XP for the half-orc fighter in the party.
In general, class and level systems are not at all well-suited for that kind of game, and you would be far better off with GURPS, or if you think you might actually be tempted to do something action-adventure-oriented, perhaps Hero.
In d&D, I would just find myself saying, "Look, you're a smart guy who is good at rumor mongering. Is there some really important reason you can't also be handy with a rapier in a dark alley, when push comes to shove?"