The only way we'll ever have changes is to get rid of the producers and hire new ones.

What works:

The age limit next year is 16 again which is good. No need for it to be younger.

Keep the categories as:
16 - 24 boys
16 - 24 girls
25 and over
Groups

I like the idea of having 16 contestants in the competition but the wildcard should be selected by the public like they did in one year.

What needs to change:

The judges:

Louis Walsh should have gone years ago. Would like actual hands on mentors who are aware of the current music scene and can give constructive advice.

The themes:
This is my biggest complaint. The themes need to be much better. Most of this year just felt like a rehash of previous years. The choices improved a couple of weeks before the final but still here are my suggestions:

90s week - 90s is the new old skool decade and hasn't been done before.
Music from the current year
Original song week - perhaps for the final five.
Big Band Week - Still like this week and don't mind contemporary songs in that style like Bang Bang.
Songs that fit your style - To see the type of artist that they could be.

Better contestant selection:
I can't believe contestants like Fluer are few and far between and she even had an average voice.

It would be nice to have more performers who aren't joke acts.

firstly, Louis HAS to go!!! DESPERATELY!!!! Cheryl too - was initially happy she was back because I did like her in 2008-2010 but this year she just came across moody and like she only came back to boost her profile back up

Bring Nicole back - I didn't realise how much I liked her until this year and I actually really missed her this year

Axe arena auditions

Timed judges vote, each judge get 30sec to make up their bloody mind, if they run out of time they lose their vote

that woman on xtra factor needs to go - bring back caroline flack

Presenter
ITV Show: Dermot O'Leary
Give him more freedom though; he has a decent sense of humour but is tied up by the autocue at the moment.
ITV2 Show: Caroline Flack

Judging Panel
Simon Cowell - 16 to 24 Girls
Nicole Scherzinger - Groups
Mel B - Over 25s
Robbie Williams - 16 to 24 Boys
Keep Louis on the panel if Robbie refuses to do the show; I think the panel needs a loose cannon

Stages
Room Auditions
(Category reveal)
Bootcamp
Each judge can set up and hold a Bootcamp to their liking. This would add some variety to Boot Camp and allow the mentor's to judge on their merits rather than a free for all. This would be an elimination stage; each mentor can take a maximum of 20 acts through to the next stage.
Four Chair Challenge
Controversial but this does cause talking points and pitch competitors directly against one another. But impose a rule and no one can be swapped back once sent away and do not have an audience for this except for the other categories.
Live Shows

Live Show Themes
Week One: Number Ones
Week Two: Best of Britain
Week Three: Born in the USA
Week Four: Halloween (I thought this week really worked this year)
Week Five: Mentor Swap
The mentor's pick for each other categories; this works well on The X Factor Australia.
Week Six: Live Orchestra week
Basically big band week but any song can be used... actually that sounds just like Big Band week.
Week Seven: From 2000 to Date
Week Eight: Public Choice/Competitor's Pick
Week Nine: Up Tempo/Ballad
Week Ten: Favourite Pre-Live Show Song/Favourite Live Show Song/New Song/Christmas Song/Celebrity Duet/Winner's single

And no more than half of the performances in any live show should be ballads.

No matter what they do or change in the show. Every single person is never going to be 100% happy.

We could have this discussion but chances are high that half of us will not be pleased no matter what/who they change.