Now we're getting down to brass tacks! I didn't explain this properly; I'll just try to clear this up as I go...
First, we're using a 32 colour palette. Now it is true to some extent that reducing some of the stages will be difficult – but in practice they can be quite drastically reduced as the arcade uses similar shades with abandon, separate palettes for different goons (with some shades from those palettes being near identical) etc. This we know.
Now we can explore a different palette for every stage – but if we do, there will still be only 32 colours tops, and the palette still has to encompass the characters. So if we've say 5 characters the palette will have to be shared between them and whichever stage. So even if we have a separate palette for every stage, the colours used for the characters will still be the same.
In practice, we can actually change the palette slightly even if the character colours are affected – this could be minimal or even quite large as long as the effect is good across the board – and Haggar doesn't end up with a blue rinse!
Colours which are unaffected by the characters can be changed with abandon – or the colours used by the characters can be re-mapped to another colour permanently if we need more for the background. We'll eventually arrive at something useable for the characters that works for every stage, encompassing the changes to the palette. But the only way to do that is to try it.
It sounds like what dlfrsilver is proposing is to have a different set of 'sprites' for each stage – with a palette that suits the stage. That's fine for HD users, but is no good for .adf.
Consider that the characters will always use the same colour registers, if you change the palette then the characters will still use the same registers – and would look very odd indeed without re-colouring them too – meaning a separate 'sprite' file for every stage!
And besides, if the aim is to keep the characters looking much the same throughout there will be a lot of repetition within those palettes of near identical colours. Granted, it may be little quicker this way, until you consider the re-colouring of the character gfx.
Currently there have been 3 adapted stages. There are palette changes in all of them. The first stage has a free colour for the goon fades as they come through the door (which is only needed for this stage). The same colour is set to red for Sodom's stage for the lighting at the top. The 'warehouse' (where Haggar first enters the subway) has about 4 palette changes. The changes are minimal but a great change was not necessary. Usually it's just tweaking a shade here and there.
So it's not really the same palette – just re-using and tweaking as much of a 'base' palette as possible, and changing the colours that are needed.
I think the best way to do that is to first reduce the colours of each stage to 32 colours, and then alter the palette to use the colour registers from the rest of the game, tweaking to suit each stage.
You will find that some of them use a surprisingly low amount of colours – I think 1 of them only used about 12! Sodom's stage re-colouring was no great shakes either...
I hope that makes sense!
I can do the colour and pixel re-working with Turrican3 if you reduce the colours to 32 per stage. It won't be that easy, if I think I can do better re-colouring 'by hand' I'll tell you! But he's ripped a truckload of great stuff already – contact him! And we already have all the character gfx.
And then maybe you can help us to tile this stuff...