>Here's the picture
>
>We have an application for a vertical market.
>
>Situation that we will be confronted to enventually:
>
>Customer asks for modifications that will apply only fot their business.
>
>Do we tell them that we don't do those or do we do it?
>
>What would be the best way to manage future developments after that customization.
>
>Because after that we'd be stuck with our glocal application but also one (and possibly more if we agree to do those customizations) variations based on our global application.
>
>What would be the best way to manage a possible mess?

Hi Denis,
our policy is
if this feature is usefull for other customers we release it in next version for all the customers in support plan without refund.
If this feature is something which is useful only for this customer we develop it and require refund.
In this case you can fall in situation where you have to manage one main version with 30-40 variants for some of the users.
We use XLS for this because sometimes we place some of the features for more than 1 customer because we adopt them to suit for their needs