I have a player who is looking at playing an Eldritch Knight. However, they would like to use the Warlock Spell List instead of the Wizard. The background of the character would be a Mercenary who got into a tight spot and made a pact to rescue himself. Know he's a somewhat reluctant champion of a Great Old One who's been gifted with a pact weapon (already an Eldritch Knight feature).

    Beyond switching the Spell List there would be no other changes. I've always thought that Eldritch Knight lacked a little compared to the other Archetypes, and this would give an interesting reason to pick it up.

    Looking at the spell list, the player is obviously giving up a lot of flexibility, but some of the warlock only spells seem ideally suited for a fighting type Character. Here's a list of the spells the EK would have access to that they normally wouldn't from the wizard list and some brief thoughts:

Eldritch Blast (C) - This was probably my biggest concern with the build. Thinking about it, there are few situations where an Eldritch Blast is going to be out-damaging a swing from a 2h weapon, especially without invocations to back it up.

Magic Stone (1) - This seems essentially useless to a primarily melee character.

Armor of Agathys (1) - This might seem a little overpowered, but realizing that the EK only has 2-3 first level spells per day it doesn't seem game breaking.

Arms of Hadar (1) - A little nice AOE damage to follow you into the middle of battle. Really flavorful and while more useful on this type of character than a blasting Lock, I don't think it's game breaking.

Hellish Rebuke (1) - Again more useful on a character designed to get hit than on a squishy ranged Lock, but still not really a bad thing.

Hex (1) - This is where is gets a bit tricky. At level 5 an extra 1d6 on both swings of a greatsword, and you get to recast as a bonus action might make this a bit overbearing. However the Con save is going to tone down the effectiveness

Enthrall (2) - EK doesn't get 3rd level spells until they hit level 7, so this isn't going to pop up for a while. However it seems tailor made for a Fighter distracting a big baddy from the rest of his group. Really Cool.

Hunger of Hadar (3) - EK gets third level spells at level 13, and at this point the 4d6 and blinded isn't huge.

Conjure Fey (6) - EK doesn't ever get access to spells of this level

Glibness (8) - EK doesn't ever get access to spells of this level

    To top this off, the EK wouldn't regain his spells on a short rest like a warlock, it would still only refresh on a long rest like normal.

    So, how do you guys think allowing a player to choose his spells off of the Warlock Spell list as an Eldritch Knight would affect balance?

Edit: I forgot to stress that the EK would still have the regular school restrictions or Evocation and Abjuration with the option for picking up non-school spells along the way.

Edit2: Again reconsidering, the list of Warlock Abj/Evo spells is terribly small, so I might actually open up the whole spell list and say that limiting the character to just the warlock list is restrictive enough. See below for the list of Evo/Abj spells the EK would no longer have access to.