So I put myself in quite the pickle.
So here's some backstory.

My first playthrough was my learning curve. Figuring out where the best stuff is, finding the vendors, who sells what, which quests to focus on, which ones to wait on. Etc etc.
My second playthrough was a power-armor wielding Brotherhood loyalist. She beat the game as brotherhood and got me several of the main quest achievements single handedly, ending her playthrough at level 34ish.

Now my third playthrough is the culmination of everything I've learned in those first 40 hours of gameplay or so as is considered my "main". Not even beating the main quest yet and is currently level 43. Now, I've roleplayed her as a sort of suave con artist who conned the X1 power armor from under the Institute's noses. But going through all the factions... She kind of likes everybody. Even her Institute walkabout led to the notion that they're not ALL bad people.
She does disagree with the Brotherhood's anti-synth nature but likes their over-arching goals.

The decision to stick with them became more solidified when I managed to convince Maxson to spare Danse (After a couple of reloads). Doing that, the only thing holding me back is the complete destruction of the Railroad, whom my character likes. Hell, I like them. And they've nabbed me some great loot. I've also already unlocked the ballistic fiber upgrades and I still carry around the Deliverer (As sneaking is her main style).

So what do I do? I've already attained the achievements for completing the game as a Brotherhood soldier. They're by far my favorite faction and I love how they address my character by rank and will mention and respect them for it.
They also have two of those refreshable quests that net me ~500 xp (together) and ~200 caps.

I love the Railroad's goals and their quests are interesting, often leading me to major loot caches and making me rich.

The minutemen are... Eh, I could take or leave them but I'm not familiar if there's really an option anywhere to "annihilate" them as the BoS does to the Railroad.

So I'm not sure what to do. Stick with the Brotherhood for a second playthrough? Save the others for future characters?

Might as well just do a playthrough in the other factions with the intent of being in the other factions as early as possible.

My first play through was brotherhood, and my second one is going that way as well. I just wanted to take more times to do stuff *pre end* before I finish main story.

It also depends on the companion you like most. Mine is Danse, so if I do a non-brotherhood Playthrough I'm not going to have my character meet him in the first place. But because mine is danse, my character is quite loyal to him, and his virtues. This means being loyal to the Brotherhood despite having my disagreements with them in regards to Danse. He would want me to advance my career with them, and continue my role as a soldier.

My hope is that someday I might find a way to give him a place in the Brotherhood again, be it through a story mod or a DLC.

My character is in a romance with Piper. She has a minor distaste for the BoS but "Piper loved that" popped up like three times during the Blind Betrayal quest. Already being maxed and with the idol perk, I doubt finishing the questline will make a major dent in her opinion of me.

I could also go pick up Curie, who likes them, apparently.

My first was Institute, and I loved it.

My second I was aimng for a BOS, but went Railroad cos everyone was going on about Ballistic armour (which shouldn't even me faction-tied imo). Then, at the last minute, I went Institute again lol

Weeellll.... I owe those topsiders nothing, most of them have been trying to kill me since I left the vault. And the institute is clean, at least

If you just purely wanted to get achievements, just start from a point in one of your previous saves right before you have to betray other factions and do alternative endings that way. It shouldn't take long. Then, you can simply choose the faction of your choice for your latest playthrough.

Makes sense, the Brotherhood have a wealth of information about the world and their mutated enemies.

Curie approves of the technological superiority.

True, but I'd still end up losing a couple hours of progress. What if I got a really cool piece of loot? I could gain a couple levels that would no longer be there on my character!

Admittedly, achievements aren't a priority. Part of why I'm leaning towards keeping with the Brotherhood.

the achievements do nothing in-game anyway, I've never seen the point of them. The only achievement that matters is getting all your settlements to 100% happyness lol

Yeah, you could just go ahead with the Brotherhood but note down a save that could act as a turning point. You might want to play out the other endings later after you've collected all the good loot that you could want on your new main playthrough. I've been going through the other endings without regret since I've collected the end game gear I want, including the two shot combat rifle and two shot gauss rifle. It certainly helps that most of the time, the legendary drops aren't very good.

My mind is mostly made up, I think I might stick with the Brotherhood.

But there's still time! I'm still fetching Curie from Vault 81, and several other quests before I move forward with the questlines.