It is a good idea, but why did you shorten it to Electrum...
Well simple:
Electrum - no sticky info
Bitcoin Wallet for Android - there is not only 1 so providing info regarding some would be like free advertising and promoting
BitcoinJ - not that often used (from my knowledge) and has a few sticky threads
Armory - has a few sticky threads
Mycelium - pretty straight forward to get: Google Play / App Store and download (a sticky might not be that relevant)
This was my logic and the only one lacking in this department is Electrum.
Not saying anything fancy, just
correct website, latest version, and maybe some important info like most frequent error, the attempt with update alerts with malware code, etc.
We are in a forum led by the community, you can create or ask to create a suitable topic as it is not difficult. AFAIK mods/Global Moderator can Sticky topics.
Will try to put together something then.
Thanks
P.S Would still be welcomed even with a "welcome message" as you can just add a link and that's it. If the future welcome message is 5000 words long it might be hard to digest, like the "terms and conditions" in most software that nobody reads or the forum rules
)