General Combat

These rules apply to all combat situations (both tactical and theatre of the mind), unless a ruling in tactical combat overrides it:

Action Economy

Drinking a potion - You may drink a potion as a bonus action, provided you have a free hand to do so. Using a potion on another creature - You may use a potion on another creature (including one who is incapacitated or unconscious) as an action. Delaying Your Turn - You may choose to delay your turn, causing it to occur after the turn of the PC who rolled the lowest initiative, but you may not use this to extend the effect of a spell you have cast past its intended duration.

Critical Hits

I dislike the inconsistency of critical hit damage on weapon attacks when you simply double the dice, especially with subclasses like champion which are built on critical hit chance for single or double dice weapons. Instead, for a critical hit, if you are rolling 3 or fewer damage dice, you can take the maximum of the dice roll, plus one additional dice roll (including all dice). If you roll more than 3 damage dice, the probability distribution curves to be much more consistent and this rule is no longer nessecary.

Great Weapon Master and Sharpshooter Feats

These feats are notorious for getting banned by DMs, but I see it is a scaling issue rather than a balance issue. I think these feats are balanced for use on a high level character with +5 proficiency bonus, where they can effectively sacrifice their proficiency bonus on the roll to hit to deal twice their proficiency bonus in additional damage, which is quite balanced for martial archetypes in high level combat. At low levels, a -5 to hit for +10 damage is broken and incredibly unpredictable with the bounded accuracy design ideology. As such, when using one of these feats, you can choose to take a penalty on the attack roll equal to your proficiency bonus, and should it hit, you will gain additional damage equal to twice your proficiency bonus. I believe this is quite balanced throughout the game. In fact, I might just consider making this a core game mechanic that all players and enemies can choose to do as part of a weapon attack, in the form of a "power attack" or "called shot" (or something like that).

Concentration Checks

I never understood why a character's ability to maintain concentration is based on their physical fortitude rather than their mental fortitude or arcane skill. If you wish, instead of a constitution saving throw, you can make a wisdom check, or an ability check with your spell casting ability modifier. I intentionally do not allow saving throws (other than constitution) for concentration checks as doing so would quickly trivialize concentration for a caster as your proficiency bonus and primary spell casting abilities scores increase.

However, if you wish to specialize in concentration, I will additionally alter the war caster feat to instead allow the addition of proficiency bonus to concentration checks rather than granting advantage. I think this will balance and scale well with the additional concentration bonus from being able to use your primary spell casting ability.