I’ve played Arcanum, but it seems I have forgotten the details. But I remember it as an interesting game, just the combat was very tedious. It’s been one of the few games which I know where diplomatic skills actually were of use.
This is a pretty late reply, but it looks like you’re a regular member, so you’ll see it eventually!
I actually think 5 or 6 is a pretty good number for basic, core attributes for a character. D&D is the classic example, with Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma. In my own tabletop RPG, I use Strength, Endurance, Dexterity, Agility, Magical Aptitude, and Aura.
The trick is combining these in different ways to get other numbers. For example, you can throw in skill ratings with various weapons and combine those with a dex stat to get different accuracy stats for your different armament options. You can then combine those same weapon skill ratings with agility to get dodge stats. (And I do this in my game, of course.) Really, you need a couple small groups of intuitive stats that interact in various ways to influence what you can do in the game. In these examples, you just have a handful of physical stats to measure what the character is and a handful of skill stats to measure what they’re good at, and they work together to create the final result, which is the number you would actually look at for a given task.
If you do ever use lots of different groups of stats, I’d suggest keeping the numbers in their own separate scales. So maybe one group of stats would typically be values from 10-20, while another group would be in the hundreds. On one hand, this could make things more confusing, but on the other, it communicates to the player that they’re not comparable – they’re not looking at an overwhelming list of equally important things, but at a few different categories that do different things, where the numbers only need to be weighed against other numbers in the same group.
Of course, the more numbers you have, the easier it is to confuse people. So, your mileage may vary.