We use the game mostly RAW. Here are some of the changes we use at my table.
Adding a small boost to Slayer Dice and criticals at Foundation, a boost to Weapons Specialist at specialization, and a change to how Martial Preparation works.
FOUNDATION FEATURE
Slayer: You gain a pool of dice called Slayer Dice. On a roll with Hope, you can place a d6 on this card instead of gaining a Hope, adding the die to the pool. On a critical success, you automatically gain a Slayer Die and add it to your pool. You can store a number of Slayer Dice equal to your Proficiency. When you make an attack roll or damage roll, you can spend any number of these Slayer Dice, rolling them and adding their result to the roll. At the end of each session, clear any unspent Slayer Dice on this card and gain a Hope per die cleared. When you take Prepare as a downtime move, you can place 1 or 2 d6s on the card instead of gaining Hope.
SPECIALIZATION FEATURE
Weapon Specialist: You can wield multiple weapons with dangerous ease. When you succeed on an attack, you can spend a Hope to add one of the damage dice from your secondary weapon to the damage roll. Additionally, once per rest, when you roll your Slayer Dice, reroll any 1s.
MASTERY FEATURE
Martial preparation: You’re an inspirational warrior to all who travel with you. When you take the “Prepare” downtime move duting a rest, describe how you instruct and train with your party. You and each ally who chooses this downtime move gain a d6 Slayer Die. A PC with a Slayer Die can spend it to roll the die and add the result to an attack or damage roll of their choice.
Design notes: at times, Slayer Dice feel underwhelming at the start of the session and it felt strange to disconnect the Prepare move to martial preparation. So using the Prepare action grants you 1 or 2 Slayer Dice (still respecting your Proficiency as the cap for the pool) since Foundation, and the D6 to another player at Mastery.