[TYPO3-dev] How to reconfigure existing config in types

[Steffen Kamper]

Hi,

i am facing a problem while using tt_content by adding a new type, 
especially with the media field (for files)
What i need is to
* change maxitems/size
* change allowed/disallowed for file extension

There is an option "$TCA special configuration" which would match 
perfect, but unfortunally this is only used for some special cases.
My idea would be to use something like this:

media;any_label;any_palette;maxitems[1]:size[1]:allowed[*.svg]:disallowed[];;3-3-3

of course this doesn't work.
Any suggesting how to work around?

vg Steffen