- Attacks of opportunity do not happen when you leave a threatened square, but when you leave a threatening creature’s reach.
This all-but-eliminates the threat of attacks of opportunity and any opportunity for mundane characters to attempt any kind of control or denial strategy. They will instead be forced to do nothing but go immediately for the kill—which is nearly true anyway, but at least trip-lockdown was kinda-sorta a thing.
- Movement can be broken up in any way, before and after taking an action.
This is a feat (Spring Attack), but Spring Attack is a terrible feat, as are the Dodge and Mobility feats it has as prerequisites. All of the above are safely eliminated from the game entirely, with Spring Attack made the default and the rest just gotten rid of. I have generally eliminated Dodge and Mobility from my games, but kept Spring Attack as a one-feat investment to get this ability, but you probably don’t actually have to. Removing Dodge and Mobility from the game certainly does make it better.
However, do note that this houserule, the free Spring Attack+, makes turns a fair bit more complicated, and predicting enemy movement even more so. That makes it even harder to have a presence on the battlefield that interrupts what enemies are doing, exacerbating #1.
- If a creature preforms the full-attack action, the creature can use its movement in between attacks.
On the one hand, the rules for full-attacks are extremely punitive towards melee characters, and go a long way towards making them vastly inferior to archers and mages in Pathfinder.
On the other hand, Pathfinder melee characters pretty much just can one-turn-kill anything they manage to full-attack. The inability to move and full-attack at the same time is often the only thing preventing melee characters from reliably killing something every turn, and this would eliminate that.
Unfortunately, the fact is that Pathfinder offers ways of its own to do that—and while they’re incredibly overpriced for a pure-mundane character, druids and summoners can get pounce (read: the ability to charge and full-attack at the end) pretty trivially. Barbarians can get it too, but it costs them a whole lot more. But once you have gotten pounce, the difference between that and what you propose is often pretty minor. The question is whether Pathfinder is better with everyone getting it free, or everyone having to go and get it. There is no real good answer to that, though: it doesn’t really work all that well either way.
So if it makes you feel less frustrated with the system, go ahead. You may have to nerf full-attacks later, but maybe that will lead to a better system overall.
I have to admit, I really just do not know of any good solution to this issue. The failures of Pathfinder melee with respect to full-attacks and movement are well-known, often complained about, and some of the most serious problems in a problem-ridden system, but nonetheless I have yet to find a convincingly-superior alternative. And since I have worked with third-party publisher Dreamscarred Press, who write the Path of War supplements that provide significant alternatives to full-attacks, I have worked with very-smart people who have spent a lot of time thinking about the problems and potential solutions.1 But it’s still a major sticking point.
Which brings me to my last attempt at a suggestion: you might actually want to consider eliminating full-attacks altogether, and use Path of War for martial characters as a replacement. The classes therein are in some ways similar to the battlemaster fighter from 5e, for reference. Path of War is not actually intended as a replacement, but it has some issues in that the “boosts” it offers tend to power-up full-attacks far more than their own “strikes,” which causes some balance issues. But using Path of War as a replacement will help a lot with that.
- There is no longer something called a “Five-foot step.” You can use your available movement to move 5 ft. at any time during your turn.
Awkward, in that it means that there is no way to avoid an attack of opportunity. Actually, though, I like this change: no way for a spellcaster to step out of a warrior’s threatened area and then cast a spell. He’s forced to either move (accepting an attack of opportunity) or try to cast defensively from where they are (risking a loss of the spell). Unfortunately, casting defensively just isn’t all that hard in a lot of cases...
- Multiple forms of movement: If a creature has multiple forms of movement, they can break up their movement. For instance, a creature with Fly 20, speed 30, can fly 10 feet, move 10 feet, and fly another 10 feet. The total distance moved cannot be more then the highest movement rate. (I am actually not sure if this is already the rule in Pathfinder).
Pathfinder is obnoxiously silent on the subject of mixed movement modes. Nothing suggests that you can’t, but nothing explains how to adjudicate the situation, either. This looks like about as good an approach as I’ve seen.
Luckily, despite the fact that I have spent quite a lot of time trying to ponder this situation and how to handle it in theory, I have literally never had it come up in practice. Characters that can fly pretty much always will. Burrow, climb, and swim speeds rarely come up, particularly in combat, and even when they do, they rarely then have you switching between those modes and others.
- Note that I was not actually a part of the team that worked on Path of War, I have merely worked with those who were. I am going to attempt to get some of their opinions on this subject, if I can.