Speed factor initiative CAN cut down on over-planning, without making play any slower, if you manage the tone and urgency well.

I have played a small number of times with it recently, after reading this article by the AngryGM (Warning: his material is written egotistically with much profanity). I liked it from a thematic perspective, as it would keep combat feeling rushed and uncertain. In practice, it accomplished that quite well. You engage all players at once for their main tactical decision, and then there is a much smaller amount of time per individual player turn. Thus, players are directly involved a larger amount of the play time.

There are some things to think about for this initiative system, though:

• Effects that last until the next turn can have wildly different efficiency. If you go high in initiative the first round and low the second, it is now a two round effect. If you go low first and high second, it barely exists at all. Possible houserule is to have the effect end on a particular initiative score.
• This CAN affect spellcasters more than it does martial characters. I had a Sorceror that chose to use Sleep, but the Axebeaks made it into melee before he finished casting. He chose to cast it at his feet rather than waste the spell. That could add cool flavor to your world (choosing the right spell for the job is tricky if you can't react fast enough to the situation at hand), but it could also frustrate your spell casters.

The last point is about your players. If they are very tactical about their combat, that may just be how they enjoy the game. Changing the flow of combat could be an exciting way to liven up the game for them, or it could destroy one of their central pieces of enjoyment from playing. I recommend trying it for a session or two, and then assessing if you will continue to use it.

Three steps to deal with this, although step zero is probably “yes, don't worry about it so much.”

1. Make sure the action is actually possible first. A character only gets one free simple interaction with an object, such as closing or opening a door, or drawing or sheathing a weapon, or jumping up on a table. Pulling out a rope (interaction #1), tying it around a post (#2), grabbing someone (action), and jumping out the window (interaction #3 maybe? + movement) is more than can be accomplished in one turn. And carrying a fellow adult — even a cooperative one — is non-trivial, so make sure that's not happening for free either: pull in the encumbrance rules and penalties on movement speed to see if they can actually jump out that window this turn, or if they maybe end their turn perched precariously on the windowsill, just in time for the thugs to get their turn.

   Also note that if the hero is physically blocking the thugs over two turns in order to fit all the interactions in, the thugs will naturally be adjacent to him and will get opportunity attacks on the hero (but not the damsel) when he moves out of their reach by jumping out the window. He also sometimes won't effectively block them if he's busy mucking about with a rope unless it's a very narrow space, because you need two hands for tying rope; thugs can just move past an unarmed hero without provoking opportunity attacks.

   If he grabs her arm and “leads her away”, then that's not going to work at all — she can't follow his lead without using her own movement, so all he's doing is Readying an action to walk with her when it's finally her turn. (He would have to grab her arm and drag her away, not using her own movement, to make it happen on his turn. And I'm sure the damsel will have words with him after — or during — such a maneuver…)

   But however it works out, let it work out how it should by judicious leverage and application of the rules rather than trying to decide that it shouldn't happen at all.

2. Notice that forced movement is a thing in the game and doesn't break any rules. Initiative is just who gets to act first; it doesn't prevent others later in the initiative count from benefiting from those actions.

   Is this an interesting way to make one character end up farther away than they could on their own? Yes, but it's at the expense of another character spending their turn in a rather sub-optimal way. (Although, sometimes the real goal is better served by doing something “sub-optimal”, so the definition of that is arguable.) Pushing and pulling others around is something you can do with your action, so there's no reason to be alarmed about it being used to improve an ally's position.

3. This doesn't end the conflict. Just because he's moved an ally out of imminent danger doesn't mean the danger packs up and goes home. He jumps out the window with her? Well… quite apart from the risk of dropping someone because you're jumping out a window and trying to hold up the weight of two people with bare hands and no climbing harness (which you might want to talk about, and maybe call for checks regarding), you still have a conflict — just not a combat.

   There's nothing stopping the thugs from peering out the window, shouting “Follow them!” and clambering down the rope too; or dropping rocks, chairs, cannonballs, and priceless bric-a-brac out the window on our intrepid heroes' heads; or hustling down to ground level to kick off a breathless chase conflict.

So yes, don't worry about this. Roll with it, take any necessary few moments to consider how to apply the rules to adjudicate the attempt, find out if it works, and then make the enemy react realistically and interestingly to the unexpected tactic.