And just hack n' slashed everyone with maxed STR and CON, but with low WIS and INT? I want to be a bad barbarian.

I know the game is intended to be played with max WIS, but I've already played the game like that and want to try something new. Without high WIS, can I still get a decent ending?

Let's see...

Since you've already played the game the "intended" way (and I assume you've explored enough to get most of the dialogue), no harm in having a little fun. This really shouldn't be too hard, because with a high CON you'll regenerate health faster, and there are some decent fighter-exclusive weapons you can obtain. (If this gets easy to the point of boredom, well... you're aware that this is not the "intended" way to play.)

"Decent ending" means "not getting killed by the final boss", so if you're confident about your ability to beat him up in melee, then go for it. In fact, you can probably still talk him into submission if you get the Blade of the Immortal from Coaxmetal.

Without high Wisdom and the extra quest experience, you'll probably have to level-grind a bit.

Keep in mind that you're still not allowed to go on a killing spree in Sigil. The Lady won't like this.

Also keep in mind that you can't wear body armor, so without magical bracelets and the Shield spell you'll have to rely on AC-boosting rings or the Dexterity bonus for defense. Then again, your regeneration might be enough to handle the damage, and you can recruit Dak'kon and have him cast Submerge the Will on you.

This is a bit off, but... I don't think it would be 'screwed', realyl. This game was made to enjoy on either way. You won't get everything... but on the other hand - wouldn't you be able to do stuff you couldn't as mage/high INT/WIS? It wasn't really 'intended to be played', it's you who decides that. It's kinda like saying 'Without Persuasion, I won't be able to manipulate people with words'. Yes, you won't be able to do that. But it doesn't mean there are no other ways, right? ;)

It might even be more fun than playing a charismatic high int character who has to hide behind words and party members because of his wimpiness.

Before I got Torment from gog I always played warrior as the game would crash when I used magic. So I still put most of points into wisdom and intelligence so I was really wimpy. Yet, by the 2nd half of the game my character started to be really good fighter and soon it become simply unstoppable. If you invest more into strength and constitution early on I can only imagine you will be even more unstoppable.

And anything you lose by lack of wisdom you can regain by beating black Abishais in the hive. So my guess is that you will be more than fine.