How can one prevent players being too character Invested?

Too Invested?
Being too invested means getting into a rutt when a character dies.
Why can't players have the same investment in their characters as the GM? I've taken this point of view, it has come to the point that I want the character randomly generated within a reasonable range for adventuring or storytelling purposes.

What works for me? Why is it ok for me if my characters die?
I am as attached to a character the way a GM should be: enough that he/she is competent and well thought out given the time constraints, but not so invested that I am not able to recoup and adapt if she/he dies. I find it well suited in games like those my GM would run, or I would also run.

As a GM I like to role-play a lot of characters, I get to play around with personalities and how they interact. I try not to role-play half-assed either, I would have role-playing notes for each character, even minor characters if time permits. That's why I'd rather have a personality generator, using key words to generate motives, aspirations, history, background, quirks etc... of a character.

I noticed the amount of time I spend on characters affects my degree of attachment. I guess that's why I have begun to like randomly generated characters, and the retro-appeal doesn't hurt. Less effort is less personal investment. The 90% of the time I should be investing would be making sense of the character and fitting him/her in the narrative of events.

Looking a my metrics of Character Investment.
If I have to make a cast of 30, 10% of which critical, 30% recurring and integral in the story, and the rest colorful dressing (reusable personalities), ideally I can spend as little time as possible with the 60% and enough time detailing the 40%. If I can make up the 60% in a few seconds, and weave their story in about 5-6mins each that would add up to ~99mins on dressing characters, 2x as much for integral characters (99mins) and about 30mins per critical character... that would be about 5-6 hours of story.

If I were to write these all down I would have written as much as 3-4 pages or 2,000 words. Although realistically I might take up some time to think about these characters. Hopefully not so much that it eats up so much time in my week or month. But usually compelling stories do, so hopefully i just draw from a bunch of stories drawn up from years ago.

Applying this to Players.
What if Players had to make a cast? What if the player had to contribute about 10-20 or so characters to the GM, and the GM, in certain points of time, will ask the Player to use one or a few of these characters?

If the player was distracted or divided enough to spread his/her attention in multiple characters, would this stop him/her from fixating over one. Maybe the GM can have a session where or pre-game exchange (play by post/email) where the player has to role-play a different character or set of them. Since there is an element of the unknown, maybe the player would set his expectations differently.

If there was fixation, I guess the GM would notice it when going through the characters and hold this character back for the players on good, until the GM feels that it was ok.

Reversing things and thinking if it were applied to me, as a GM I guess I would have no problem. As for career players, what comes to mind is a friend of mine who would "exploit" the multiple character option our GM offered to reduce the effect of character death on the pace and fun of the players. I know he would be disappointed, especially if I denied him the more powerful character and employed it for my own purposes...
...maybe the option to employ certain characters for the GM's purposes would reduce fixation even further?

Knowing what to do in the Future: something to try out.
I guess having this written all down, in the future, I should have the players share the load of NPCs generation. Not only it would drastically cut down the amount of time I need to sufficiently detail the game's cast, but also create a reserve of characters in lethal games.

Players who don't make characters.
Have another player make his characters. I sometimes make characters for my players, which I optimizes expectations but is a bad habit. If I have a random character generator, I'll have the player use that instead in the future.