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.
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.
Trophy: When you defeat an adversary of your tier or higher, you can take a few minutes to collect a trophy and gain a Hope. While carrying a trophy, your Slayer Dice pool maximum increases by a number equal to the adversary’s tier.
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. The idea was to raise the pool by 1 to 4, following character Tier. Additionally, you still benefit from a critical success: you can use the Hope you gain to get a Slayer Die, which brings the total to 2 Slayer Dice if you need them. Moreover, it felt strange to disconnect the prepare move to martial preparation. They are now one.