Hmmm. Sounds a lot like Skyrim actually.
Funny you mention that because Skyrim makes a pretty good case for being able to use shit you aren't specialized in - you can get disarmed, enemy melee attackers not infrequently decide to grab their fallen comrade's ranged weapon when they have no chance of reaching you directly, despite not being good with it and so on.
Unless you have a readily useful natural weapon you may have a perfectly good reason to pick something you are not good with at some point.
Another funny thing about Skyrim is that it involves pretty decent system naturally limiting swinging and casting - you need hands to cast spells. Some can be cast with one hand, some require both.
Ability to do so also removes artificial contrivances from the picture when building quests and plot.
Want to put on faction's armour to impersonate someone or maybe a suit of armour that has been built enchanted specifically to allow survival in some sort death-zone no spells cast readily in the field can shield you from, or maybe need a hammer made and enchanted by long extinct mysterious race to whack the heart of dead god and a matching armoured gauntlet to be able to hold this hammer without your eyes boiling out of your skull?
Nigga, pls. You're a mage, you can't use heavy armour or warhammers because your class restrictions say so.
Problem?
Do note that two out of three examples above appeared in Morrowind, one as obligatory plot point too.
Why? Because a mage can do more damage with great sword, that he can hardly lift, than with a dagger? That would mean that the game doesn't need any daggers at all then, because bigger is always better under any circumstance.
You're retarded, seek help.
Even in degenerate damage centric systems there is far more to weapon selection than just damage - you have speed, reach, encumbrance, bonuses and maluses from ease of use, additional effects such as different knockdown chance or different damage types and their modifiers.
Still, I get where you are coming from, but a scrawny little motherfucker like a mage does not carry a great sword and full plate mail around with him "just in case he needs it".
Full plate and GS are pretty fucking heavy. Such mage will have problems carrying other things he will needs unless endowed with high STR, but this demands sacrifices to be made when building this character.
GS makes for a pretty bad last resort weapon too, because it's harder to draw quickly and when something is in your face it's already too close for GS. In general good system should encourage almost all characters to carry daggers as backup weapons.
It's not "ARBITRARY RULES!!!", it's simply that they dedicate their time to studying and practicing magic, which is physically and mentally exhausting. Or is it?
But still find time to clear dungeons and mountains, or travel on foot through forests... but no he can't lift a sword and "stick them with the pointy end"
I dare say that there's more to swordfighting than lifting it and sticking the enemy with the pointy end, but I'm an amateur in the field.
It is sticking the enemy with the pointy end that does said enemy in, though, and even a complete amateur can do that.
Trickier parts generally involve avoiding enemy doing it to you and bypassing enemy defense, but we aren't talking about mages participating in clean 1-on-1 sword duels with warriors. We are talking about mages picking up a melee weapon and sticking it where it counts or when they are desperate enough.
In general no generic, human produced weapon or armour should have hard stats requirements either, meaning it should be technically usable by anyone.
But then, there is also stamina. Anyone can put on a suit of armour and walk around in it, or pick up a heavy weapon and swing it a few times. The problem is when you have to keep that up for prolonged periods of time.
Of course, heavier weapons should have maluses depending on strength, something like flail should give you ample opportunity to crit yourself if you try to use it without skill. Speqaking of maluses - speed of an attack and attack rate are fucking important, especially if you can interrupt enemy actions with successful attacks.
Also, I'm longing for combative mages who aren't frail dudes in bathrobes going against hail of arrows and shit.
Assuming that mages are relatively rare and powerful, they are very obvious targets. This means that if you're an adventuring mage, you either:
-avoid direct confrontations as much as you can, especially if they are actual battles with lots of people fighting
-put on the heaviest armour you can carry, preferably boosting it with magical defenses because you can be sure as fuck that every enemy with ranged attack will do their best to hit the guy who mutters and waves his hands around
-are very, very dead
Main archetypes in such game would look as follows:
-bathrobe mage - frail scholar dude, may or may not be a viable adventurer, but is generally not a viable combatant, will use diplomacy guile and trickery as often as possible to avoid being face to face with someone with nasty piece of steel
-battle mage - less frail scholar dude, wears heavy armour to be viable in combat, is much less mobile than warriors due to having to sink a lot of his potential into developing his intellectual and magic skills and not being in shape to run around in plate armour, poor stamina, sucks at melee.
-warrior - armoured dude, heavy hitting, durable and mobile
-archer - less armoured dude, good at fighting at distance
-thief - sucks at combat, good at stealth and subterfuge.
-monk - extremely mobile, but depending on being as unencumbered as possible. May be lethal in low numbers encounters and against slow, but heavy hitting monsters. Gets murdered if there are more arrows in the air than he can deflect or weave between.
-assassin - like thief, except less diverse skillset and good at stabbing or sniping someone unsuspecting then getting the fuck out.