I'll repeat some things, and add others.
Do it.
As Ary pointed out, activity over weighs logins. Add an invisible scoreboard for different ranges of players (based on active days: 0-30, 31-60...) and reward them accordingly for the different tasks they perform.
Example: say one need write 10, 20, 50 chat lines in one day. This can be conditioned further: if (s)he has the required number of chat lines, and that number ranges between, say 10 and 90% of the total lines in the area, he gets a +1 in "loudmouth" for that day. I didn't say 100% because that would represent a monologue.
Now, alt abuse can occur, such as someone chatting with themselves. If the chat lines in a scene come ONLY from the same IP adress, they don't count for either. If other addresses are involved, they count and are calculated for each alt based on proportions mentioned above.
The following day, each player gets a fix reward as stated a few posts above: attack if they have the most won attacks, defense if they won the most attacks on them, volition (which needs to be finished as a concept, first) if they spent enough APs while moving and so on.
Furthermore, once a month, give out temporary titles to the one with the best score according to what they did: attack - fighter of the month, defend - defender of the month, walk - strider of the month, sacrifice - killer of the month, chat - loudmouth of the month and so on, along with a stat bonus which represents the category they won.
I went into detail because the chat example is a tricky one to make work, but there are ways to do it. Others, such as combat related ones are easier.
Just imagine a new player waking up one day with a title saying "Fighter of the Month". I call that incentive. :P