Why did Gendo want to get rid of the Spear of Longinus?

Question

In episode 22 of Evangelion, Gendo authorizes throwing the Spear of Longinus into space at an angel in order to defeat it. The dialogue indicates that Gendo is using this as an excuse to get rid of the Spear, mentioning Seele's mass production of Evas.

Kouzou: Ikari, I still think it's too early to use this.

Gendo: The committee has already started to mass produce Evas. This is our chance, Fuyutsuki.

Kouzou: But

Gendo: We cannot make time run backwards, but we can spur its course forward with our own hands.

Kouzou: The old men won't allow this.

Gendo: Therefore, we must finish this before SEELE has time to act. It is not acceptable to lose Unit 02 at this time.

Kouzou: But you can't use the Spear without SEELE's approval.

Gendo: The need is the justification. There are no other factors to consider.

Kouzou: Justification? No, what you're looking for is an excuse.

^{Ep 22 Transcript from Forever Dreaming and Animanga}

In the next episode, Seele indicates that they see the Spear's use as a potential sign of betrayal, again citing the incomplete Eva production.

Seele Member: It's impossible for us to retrieve the Spear of Longinus.

Seele Member: Why did you employ it?

Seele Member: The Eva series has not been completed as per our plans yet.

Gendo: I gave priority to the destruction of the Angel. It was unavoidable.

Seele: "Unavoidable?" Your excuses need to be a little more convincing.

^{Ep 23 Transcript from Forever Dreaming and Animanga}

Why was the Spear of Longinus important to Seele's mass production of Eva units? Why did Gendo want to get rid of the Spear?

Answer 1

According to a the Classified Information and the SEELE ending of the 2nd Evangelion game, it was less something of importance for SEELE's plan and more of a potential threat

Rather than forming a sea of LCL, SEELE wishes to be merged inside an Evangelion unit with its own S², after destroying the Spear of Longinus. By placing their own souls within the body of a godlike being, and destroying the only weapon that can harm the body, they would effectively create an immortal God with a human soul which would represent the pinnacle of human existence, and live through all of eternity.

Source: Human Instrumentality Project > SEELE's_Plans

By recovering and holding onto the one weapon that could foil their plans, SEELE mitigates the risk of it being hidden away and later used against them, especially since in the game SEELE destroys the spear, something they can't do if they didn't know where it was or couldn't reach it

it is important however in Gendo's version of the Human Instrumentality Project

It finally returns in Episode 26' after reacting to the awakened and freed Evangelion Unit-01. It proceeds to become an important tool for the Human Instrumentality Project and merges with the Eva, creating the Tree of Life.

Source: Spear of Longinus > Third Impact

though we don't know if Gendo knew for sure that it would return