You are proficient with it.

While a warlock is only proficient in "simple weapons" you can create any melee weapon and you are proficient with it. Martial weapons often are stronger and have other abilities.

An upgrade for your Mace would be a Flail or a Warhammer which all deal bludgeoning damage, but martial ones have 1d8 instead of 1d6 as damage dice and the Warhammer can be used two-handed for 1d10 as damage dice.

You can create one as action.

This means wherever you go, you are never without a weapon.

You can switch the weapon type to fit different situations (sometimes you might prefer a weapon with reach or a different damage type, keep in mind this feature is lost as you bond to a specific magic weapon).

Also you can indeed create throwing weapons, because they are basically melee weapons with aerodynamics. So while taking a whole action to recharge, you are never out of ammo.

It is magic

In early levels you might not have a magic weapon when fighting against a creature with immunities or resistances versus non-magical weapons. This weapon overcomes such resistances.

You can bond to any magic weapon as pact weapon

This is not restricted to melee weapons, and you have the weapon always ready.

Invocations

Lifedrinker and Thirsting Blade benefit you with abilities you can only use with your Pact Weapon.

Yes, but you have to be level 12 to do this

The Sage Advice articles says:

You can also use Pact of the Blade to bond with a magic weapon, turning it into your pact weapon. This magic weapon doesn’t have to be a melee weapon, so you could use the feature on a +1 longbow, for instance

This takes care of the ranged pact weapon, and allows the use of both Thirsting Blade and Lifedrinker with a ranged weapon. This means you can attack twice with your Attack action using a magic ranged weapon.

And the Sage Advice compendium says:

Does Crossbow Expert let you fire a hand crossbow and then fire it again as a bonus action? It does! Take a look at the feat’s third benefit. It says you can attack with a hand crossbow as a bonus action when you use the Attack action to attack with a one-handed weapon. A hand crossbow is a one-handed weapon, so it can, indeed, be used for both attacks, assuming you have a hand free to load the hand crossbow between the two attacks.

This allows you to attack twice -- once with your action, another with your bonus action. Since you have Thirsting Blade (which works with any weapon as long as it's your pact weapon), you can get three attacks in all.

However, while Thirsting Blade is available at 5th level, Lifedrinker is available at 12th level. So to complete this build, you have to be a 12th level character at minimum. Most of it, you can enjoy from 5th level onwards though, as only Lifedrinker is the high level component.