I have just had to deal with this - AGAIN - and would like to rail for a moment, hoping to provoke discussion to promote change. I posit that this is big enough to deserve a Foundation-wide venue for initial discussion so am including Wikitech-L.
Most of us are probably familiar with the cycle:
Person A on en.wp (or, any project) uploads an image which is apparently public domain or free use by any reasonable standard. It gets put on article X. There is much rejoicing.
Person B later thinks "Oh, this is something other projects might use, and it's 'free', so..." and uploads it to Commons. It then gets deleted at en.wp by a helpful bot.
Person C on Commons later identifies that it fails to be an entirely free piece under the much-stricter Commons rules, due to some factor that A and B were unaware of. Person C nominates it for deletion there. Poof. Gone.
Now, we have NO image, for something that is sufficiently legal under our rules and the law for use on en.wp (and likely, most of the rest of the projects). A delinker bot helpfully comes along and nukes references to the image off the pages that used to have it. Maintainers who miss the bot edit fail to notice that it's gone. Many months or years go along and finally someone notices, and either is an admin and restores the image on en.wp or finds an admin who restores it on en.wp.
Now, for someone who sees images as an integral part of the total READERSHIP value we present, in terms of helping people understand things by drawing their attention and expressing ideas and history in a visual manner, the long periods where we've lost all image are mind-numbingly counter to our core mission. That we've evolved into this cycle due to bureaucratic friction does not make it acceptable.
PROPOSED: This is not acceptable. Something must be done.
SUGGESTED FIX #1: Create a parallel "Uncommons" project, for shared images which meet minimum project legal non-copyvio standards but do not meet the threshold Commons is insisting on (or we have defined Commons to be). This requires coding in the WMF to allow a parallel project as image source, and would require that Commons' deletion process be modified such that deletions for copyright niggles be a shift-to-Uncommons rather than an outright delete.
SUGGESTED FIX #2: Stop deleting things from local projects when they're uploaded to commons. This requires additional diskspace from the Foundation (by some as-yet unknown amount). Ops team - Could you attempt to determine if this would be significant, troublesome, small enough to not be significant, etc?
These are not the only two possible solutions, but they come to mind immediately (and have previously when I thought of this). Additional fix concepts solicited and welcomed.