Would this be weird in a soup?

[MooDeng]

If I chuck it all in together?

3 red peppers
2 onion
Carrots
2 potato
Red lentils
Leeks
And a cooked chicken thigh?

No.

Sounds good to me op,I'd eat it

I might shred the chicken thigh or something. Just floating around in the soup might feel a bit odd. Would still taste OK though.

(short and sweet, heh. I'm sure it will be fine; I often make throw-it-all-in soups and they always turn out tasty)

I reckon it will taste nice. I have a thing about bones and chicken in soups. I would have to have the thigh in some sort of soup bag separate and then add cooked shredded chicken last.

Sounds really good.

Oh yes I will shred the meat

I think in my head the lentils and peppers make a soup

And the winter veg and chicken make a soup

But wasn't sure about it all in.

The beauty of soups is that you can throw just about any pulse, bean, veg, meat into a stock or not, just salt seasoned water or with bouillon, is great. Spices if you have them, s&p if you don't.
Short answer: No...does not sound weird at all; sounds good, season to taste.
Thicken with corn flour/water or instant potato flakes.

Dm used to do what she called "left over veg soup" like that. It varied how nice it was.