%% Not multiple edits on same template %%
I think the edit page sould be more smart. If a user open the same page two times, the second time sould be warned that the page is already opened. This may need some trans-window comunication, that is not something browser love to do, but I guest is possible with DOMStorage/Cookies or something else.
%% Autosave feature for edit %%
Again, in this day and age, losing data because a computer crash is a problem that sould never ocurr. The edit page sould save the latest version of the edited text to a local persistent area ( DOMStorage? ). That way, I can 'accidentally close' the edit page, and wen I reopen the edit, the page sould detect "He.. the page is on the same revision, this mean my edited version is interesting", and let the user continue editing. "You closed the edit page withouth saving. Do you want to continue with the old version?". Somewhat like the "drafts" feature on gmail, or the autosave feature of OpenOffice.
%% Edit in the browser any fileformat wen webeditors for such fileformats are available %%
Wen possible, documents sould be editable inside the browser. This mean as possible, add a SVG editor or a Math editor or a HTML editor or a DOC editor or a PNG editor. The PNG is wrong -> download -> edit -> upload is lame. The PNG is wrong -> edit -> save is cool.
The current edit page only supports wikicode :-(
%% Un-cruft mode %%
There seems to be a lot of "META" information on the wiki, all this metainformation like "stub", etc.. sould be optional. There must be a single checkbox option to disable it all. I don't want to read even 1 more "citation needed" or "this is a stub" bloat. Maybe default sould be to "show cruft".
%% Wikipedia Green, Blue and Orange %%
A way to fight Deletionism, could be to have something like "different levels" on the wikipedia (a wiki). Set a group of pages on "Book Blue", for pages with a maintainer, and pages approved by a superior committee of quality. Set a group of pages on "Green Book" for pages that serve the merits of notability. "Yellow Book" for pages that don't fulfill a notability criteria. Deletionism is binary, computers can work with more values than 1, 0. Hell.. you can make Green Book and Yellow Book invisible for the un-loged users, only available for loged users. For this thing to work, Templates sould use different colors for differents books. Colors will also account for quality. The german will be mostly blue, while others will have more green pages. There will be a wiki with 90.000 green and 10.000 blue. And other one with 10.000 green and 90.000 blue.
%% The Death of Wiki %%
Ultimatelly, al wikis lose the war against entropy and are abandoned. This will hit all wikipedia wikis, and all based on mediawiki. While you can't stop that, you can code something so the resulting dead body of wiki is not pure shit. A possible idea could be to "auto-protect" pages without edit in N years (4 years), and save id of the "last know good version", this can be done flagging the pages as "dirty" after a edit, and flag pages as "clean" wen a logged editor say so. Something like "Page Milestones". Maybe the "History" view of a page sould list first the last 10 milestones (newer first), then the "dump" of all edits. There are probably about more than 10 years to think about this issue.