Yup, DW Basic was out at that point so that was the original audience.  Level up as you will.

It's cool to present custom moves in a variety of ways.  For example, you could print it out on a card and slide it over to them when they enter the room.  In this case, you're telling them something about the pools and it's kind of a dare or a temptation, right?  Want to really tempt them, just write out the trigger and show them that-don't show them the rest of the move unless they trigger it.   Other times, you could wait till they triggered the move, then show it to them, and then ask if they're still sure that's what they want to do.  Here, showing them the move is like them beginning to do something and then realizing how things could go down and what's at stake.  Other times, moves are about stuff they already know, you're just telling them there's a mechanism for it - for example, if the characters are out in a blizzard and you have a crossing slippery ice move, the characters know what ice is all about and you can put that out at the beginning of the session. 

Cavalier playbook please!  Actually, that sounds like a compendium class rather than a playbook.  Well shucks, I guess I should put my money where my mouth is.  How does this sound?

When you bolster your relationship with your mount, you may take this move the next time you level.  

Time in the Saddle
Write a new Bond with your mount, this Bond can be resolved as usual if you so desire. Whenever you write a new Bond you may write it with your mount.

Once you've put Time in the Saddle, the following moves count as class moves for you.  In addition to your normal list of moves, you may choose from this list when you gain a level.

Practice Makes Perfect
When you bolster your relationship with your mount, add your bond to your hold.

Two Heads
When you make a move that involves your mount, you may roll +bond instead of the normal stat.

Do the Same for Me
When you are incapacitated, unconscious, or dead in the presence of your mount, your mount can make basic moves on your behalf.

Thrown from your steed and taking damage is like two hard moves (use up their resources and deal damage).  Why would you choose that option?

I'm doing something similar in my current game.  The paladin works pretty well if you think of recalling your vows or reciting the word of the law as a prayer.  Lay on hands can be a pat on the back and a reminder of duty (the increase in hp is about renewed readiness for action rather than magical healing).

I had a lot of fun last time.  DW plays really well as a PbF.

I would encourage you to read 'signature weapon' as 'signature weapon system.'  A two handed sword, rapier and main-gauche, short sword and buckler, and long sword and free hand are all distinct ways of fighting with pro's and con's.  If they want two swords as their signature weapon [system], it has everything to do with the fiction and nothing to do with the mechanics.  They're going to do their class damage+enhancements no matter what their signature weapon is.