Thanks for the suggestions!

Groups be established so like-minded people can join together for better sharing and discussion of topics they are most interested in

I assume you are looking for something like Facebook groups. Can you please elaborate more on what you are looking for for though? There are currently tags, which organize posts via topic, and Steemit.Chat groups where people can go to discuss topics they are interested in (outside of posts). These two things do seem to cover a lot of what you get from Facebook groups. I'm not exactly sure what people would be looking for beyond what is there today.

User profiles to include pictures, external post links (to instagram, facebook, twitter, etc.), optional personal profile data

Good call! Added :)

Basic email messaging system so users can email 1:1 each other or 1:many (group emails)

This is basically there as "SteemGrams ". Its not exactly email, but it covers the same requirement of direct messaging. Hopefully it will be even better :)

Blocks/spam flags to limit misuse

I added this as well, although this could also be 'fixed' if they implemented the feature to charge each user postage to send messages to unknown users. (Spam me away, if I get $0.25 SBD per spam!)

[Edit] It looks like you added some more. I'll review and respond to those now :)
[Edit2] Reply below :)