You're not discussing just basic hacking a host, you're discussing a host-focused datasteal, based around Matrix Search and copying files. Which doesn't make sense anyways, because Crack File is an Attack action and so there's no way to do it other than alerting the spider to which file you're removing protection from! All the things you mentioned about the spider just immediately knowing you attacked a file apply to literally anyone. What's to stop a spider from just going "You removed the protection, I put it back on, you removed it, I put it back on, you removed it, I put it back on." If your answer would be "They're not marked as the Owner, and so can't put the protection back on it", then I'd like to point out that they wouldn't be alerted to attack actions against it either, then.
Crack File is an Attack action, so yes, the Spider could put the File Protection back on the Icon as a reaction. However the RAW is that the Spider only knows a successful Attack action targeted that Icon. Could be Brute Force, could be Data Spike, could be Crack File, or whatever. The Spider really should have to spend an action using Matrix Perception to figure it out. But yes, a Dick GM can stop all Matrix Data Steals forever. They could do that anyway, they're the GM.
And if the Spider isn't considered the owner of every Icon in the Host I think the Matrix breaks in a fundamental way. That's wandering towards hand-waiving territory that the Matrix rules rely on.
And if you're just taking a tour to check out the host Architecture, fine, but if you actually want to do something you typically need to find the Icon associated with that thing. Be it a Data Steal, Elevator Controls, or whatever. Unless you're conveniently using Direct Access on the thing you want to Hack anyway (which happens a lot) you still need to do a Search to find the Icon to do a thing. If you need to find multiple Icon's to do things you're spending a long time in that host. The more dice rolls you have to make the greater the chance of failure.
And if there is a Meat space component to your run you've just tripped the Alarm.
Once you take out the spider (don't ignore this), you don't need to worry about your marks being removed.
It's simple risk avoidance. If doing A always creates a risk, and doing B sometimes creates a risk, unless the risk created by B is catastrophic failure, you go with B. Starting a Hack with an Attack Action always alerts the Icon Owner once you get a Mark. Brute Force doesn't give you a better chance of getting a Mark than Hack on the Fly. If Brute Force had a greater chance than Hack on the Fly in getting that initial Mark it would be a different story.
The risk from a failed Sleaze action is that the Icon's owner responds with an immediate Data Spike that Bricks the Deck in a single shot. Which isn't really a big deal, one hour later you can try again. (Presuming the Decker has a Hardware skill and toolbox anyway....). As long as the Deck isn't Bricked, Re-boot (or Erase Mark, whatever), and try again.
Absolutely you can take out the Spider. The Samurai can gun down the rent-a-cops on site too. But starting the Run with "Roll initiative" is usually a terrible idea.
Again. Hilarious concept. I've thought about making similar concepts, it just boils down to Brute Force requires another skill to be maxed (Cyber Combat) and another Matrix Attribute (Attack) that Sleaze focused Hackers don't have to invest as much in. And it doesn't increase your overall chance of Success. (arguably Hack on the Fly could have a higher limit so would have a greater chance of success overall, but....) And actual play would take forever since you immediately drop into initiative passes, but as you mention, don't play this build 'cause it's a dick move.
The real key to the build is the silly high levels of dice to oppose Matrix Perception, and that benefits a Sleaze based approach just as much.