If there were a site that just hosted PDN plugins, you'd have to make sure they were worth their sever space & worth people's time & HDD space to download. If they were tested in the Plugin forum & then ok'd to go on the plugin site it would be good. Otherwise people will open pdn & it'll say a new plugin is available do you want to download it? For all they know they could be downloading the best plugin ever or some pile of rubbish that soemone made as a test to see if they could even do it.
I guess what I'm asking for is quality control. It's no good having a dedicated server / website for paint.net plugins only for loads of them to be rubbish. They should be tested beforehand by regular members of the forum that use paint.net a lot so that they can suggest what the plugin needs before it goes on the plugin site. What would also be needed on the site, would be categorization, it's no good having a massive list of plugins & a brief description, simple categories would suffice, things like Distort plugins, Render plugins, File Types, Adjustments, you get the idea.
Anyway, I'll shut up now & let y'all contemplate my blatherings