So plugin it is and it's good you noticed, that creating the plugin for built-in IM needs to be consider both ways, first, learning skills to write own apps/scripts/plugins or whatever comes to need, second, tearing apart somebody's work, to learn the "maintenance".

And here it comes, 770 and n8x0 devices are literally dead, but as you noticed that is good, for already mentioned reasons (It's like you're reading my mind, endsormeans )

I already have to thank you for all comprehensive answers, it's been very helpful and motivating.

Coming to the essential of this post:

Flasing was the first thing I did after I get my 770. Already tried all I could get without old OS2005 images, to be exact, I tried 3 Images of os 2006, 4 of OS 2007 and now Im working with 2008HE OS but Im considering coming back for Latest fiasco of the OS 2007 Hacker Edition, why?
You should know, OS2008 it's the latest we can get for 770, and it have more need for performance than OS2007, not mentioning the older OSes, so it can cause troubles sometimes. Secondly OS2208 it's not end-user operating system, sometimes it's gets annoying, for example yesterday I discovered that I cant set clock alarm
But, there is always but, yeah?
Repos for 2008 are much bigger than repos for older versions. I found the Pidgin and Pidgin Facebook chat plugin, that's good. Bad is, I can't install pidgin, because of the missing libhildon-extras1_0.9.7 package. I couldn't find vaild package though the web, but I didn't try much.
Still, I will install it eventually, and will report it here.

About symbian, yep, that's what I though.
About java, my 770 screaming without those apps, just for mentioning it

For the 3rd..., We already mentioned what was needed, didn't we?

I bet we do

Edit 1

And little off-top, I cant wait when the neo900 get's into my hands, but I promised myself, that I won't get it before I'm done walking though older devices (Without N900, I think I have it all workout )

Edit 2

I just came up with idea that sounds nice, but more I think about it, Im getting more "no"'s than "yes".

Maybe we will be able to create a update-patch, a small one, that will bring up 770 to 2015

I mean some package that will provide support for sites, chats, and thing that were created after the nokia 770 was released.It sounds great, but, do we:
1. Have enough man power and people that would get involved here?
2. How much time would it take? People can get involved but without proper knowledge it's simply won't work out.
3. I have some expirience with going through linux right to the center (The kernel), but I was long time ago. Still I have more expirience with Debian/Ubuntu than with any other linux. My knowledge can be refreshed, but it's not all, patch won't make itself to existance.
4. Bringing up 770 or going with idea and go with n8x0 as well, but how to get people involved? That is probably the hardest part.