Preventing player elimination

Most people do not like to be left out a game half way. With 2 player games, the game simply ends.
But in games like Risk or Monopoly, a defeated player simply can only watch. Now, what are the ways to prevent this? It is to keep players in the game even if they are defeated. Or the game ends once 1 player is defeated.

Although I know of people who like the taste of defeating multiple players. Thus the need arises to continue the game after 1 "casualty".

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Here is my approach.

In my war game (max 6 players), players have several tiers. In the first tier (tier 0), the basic tier, they have a normal army and normal resource gathering.

But once a player is wiped out or have given up. They can come back as a (often smaller) mercenary army, in tier 1. The units then are more powerful through a bonus of XP that units can spend on their statistics right away. Approximately + 16,7% for each tier. Thus 6 soldiers are as strong as 7. Further, they have a small base for production, but lack income. They need to receive money from other players.

And tier 0 players could hire them to do the fighting for them. When there is only one tier 0 player left, that player wins. The rest are simply ranked in the tiers they are in. Secondary rank is army size with gained XP.

Every one can keep playing. And in a way, there are multiple winners. Whereas the last player is the true winner, the last defeated player comes in second and the best mercenary comes in third.

Another approach
Is that there are 3 players and 3 mercenary from the start. Then once a player is defeated the game ends. All scores are added up to determine 2 winners. 1 winner in the player pool and 1 winner in the mercenary pool.
This also gives 2 worst players at the same time. So the biggest loser is never alone.

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Play test results:

A 3 player game. All 3 of us are players.
Whereas I was on the winning side. My 2 friends had trouble facing me. Already they teamed up. Yet I managed to destroy the base of one of them. I retreated to tend to my wounded.

He had no more income, he was only left with some defence structures. And his last remaining units where some slow and heavy damaged Infantry and Tanks. Simply a game over for him. However, I intended to keep him alive so he would not return as a mercenary. Unless he would admit defeat and give up. And then return as a mercenary.

But he decided otherwise. He simply asked my other friend to kill the remnants of him so that he would gain XP instead. He did not retaliate to being killed. And my other friend saved up money. Afterwards he himself returned as a mercenary. And got all the money that was saved up. Thus I now had to face 2 opponents. Both with extra XP.

I clearly lost that game afterwards. But all was fair and just according to the rules.

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A 4 player game. 2 Players, 2 mercenary.
The 2 players where building up their bases and defences. Clearly not wanting to spend their resources on the mercenary. Thus I and my friend where just sitting there waiting. One of the players didn't even want to hire us. And this reminded me of a game Kings and Knights on Starcraft. Where the players sometimes simply ignore the knights presence.

Luckily the other player spend some remaining resources on us. Just enough for me to get a Mortar Jeep (Fast and sufficient Range). I started harassing towers and got my Jeep twice as strong before my opponent had the right defences.

My friend however spend the resources on some Grenadiers. And clearly took losses right away. He did not fret. And simply said, I give up. Thus he became tier 2. Then he said, I give up again. And again, etc.
He said, how about I become a god mercenary. Want to hire me now?

According to the rules, he has to wait 3 rounds between every tier. Thus having +100% takes 15 rounds for a starting mercenary. Even though I won as mercenary. I lost that game; my game.

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2 play tests, 1 success, 1 failure (in my eye's). And 1 failure means a complete failure.

I need to revise the rules? I can't let a player give up over and over again. So that he can return twice or tree times as strong. Even though it takes time according to the rules. And this player clearly lost in a way. It destroys the game play.

Suggestions for tackling that problem?
- One of my friends suggested having longer and longer times waiting times between each tier. 1 round often takes 5 to 10 minutes if actions are taken. Having 15 rounds means 75 to 150 minutes. If it is 3 rounds for tier 1, then something like 6 rounds for tier 2? 45 rounds sounds like an awful lot.