nlimited unit selection and MBS would radically change the game. It's not something I'm pulling out of my ass, it's the truth. You're adding/modifying mechanics that weren't in the original that would completely change the way the game is played, creating new strategies and rendering others completely useless. It's not a good thing to do for a game that is 18 years old and is played by people who know everything there is to know about it and still come up with interesting tactics. It's just like if you changed chess so you can move all your pieces at once. MBS would allow players to create units en masse without having to manage their base at all except for building additional structures or assigning building to groups. You'd see a swift switch to micro management instead of the great balance between micro and macro that's in BW and that makes it so exciting.
Just FYI, I've both played and watched competitive BW/SC2 for many years now. And by, "played", I mean at a pretty decent level - B on iccup back in the day, and Master league in SC2. You can assume I have a clue about what I'm talking about and skip all the dumb chess comparisons and general platitudes.
Unlimited unit selection would make moments of panic much rarer and less prone to mistakes. This is when you see if a player is really good or not. Being able to control only 12 units per group has a huge impact when you're caught off-guard and have to retreat or move to another position. You have to move all your units the best you can to avoid heavy casualties. With unlimited selection you can just 1move and be done with it. Marine & Medic armies would move far more efficiently with unlimited selection and you would also be able to stim all your Marines at once instead of having to actually select them group by group and then stimming. Zerg players who play with Lurkers sometimes count on the Terran player to mess up moving their units out of the spines range. Same goes for Reaver drops into worker lines. You often have more than 12 workers in a base. Select them all and move them away and the Reaver attack is far less threatening all of a sudden. Psi Storms? Just move your whole army away from them instead of having to micro the units actually caught in the storm, which requires effort. While you're not micromanaging the rest of your army, the opponent could land another storm and you wouldn't have time to react. Storms behave rather differently in SC2 and are much faster to compensate for the unlimited selection. And also, like you said, MBS + unlimited selection would make Zerglings unstoppable unless there are massive balance changes, which would further change the game.
Also deathballs in themselves are not the problem. There are deathballs in BW as well. The crucial difference between the two however is that you can't move your deathball as one entity in BW while you can in SC2.
I really think you're confusing the effects of unlimited selection and pathing. The Marine/Medic point is somewhat valid, but only for the same reasons as the Crackling one - with unlimited selection, large armies of low-supply units would become easier to control. However, having a 60+ supply army in one control group doesn't help much at all in most of the situations you're describing, primarily because of BW's dreadful pathfinding.
In most situations, you don't *want* to stim all of your marines at once - with a large army you won't get more than half of them to attack at once anyway, and stim is very expensive. You don't *want* to select all of your workers in the event of a Reaver drop - it'll just bunch them up, making it easier for the Reaver to score a big hit; good players don't even do this in SC2 vs mine or hellion drops, because it's not effective. You're not aiming at losing no workers, you're aiming at the scarab hitting a single worker. The idea of moving out of a psi storm by selecting your whole army and clicking away is simply laughable, your units would trip over each other while still standing in the storm area of effect - you don't normally use control groups for dodging storm, or plague, or any aoe effect, because it's much more reliable to quickly select what you need and move it manually.
Let's look at deathballs for a second. The proverbial BW deathball is Terran mech. Does having a 80+ supply mech army in one control group really change much? You still need to leapfrog your tanks. You still need to control Vultures separately and manually lay mines. You still need to ensure a nice Goliath spread on your frontline to avoid drops and other tomfoolery. So what exactly changes? If you just want to move an army across the map, you do 1a instead of 1a2a3a4a.
Putting aside potential balance problems with Cracklings and Terran Bio, I feel like the most these changes would do is provide an accessible "good enough" option for more casual players. One of the problems of BW is how high the initial barrier of entry is - the game is not that difficult to play after you train yourself to take care of all the APM-intensive busywork, but before that, it just feels like shit.
For the record, I think BW is the best competitive RTS of all time, and massively superior to SC2, not because of UI specifics, but because of the excellent unit design and economy balance (and also maps, but those aren't on Blizzard). At the very minimum, I'd be very interested to see how it would play with a modernized UI.
Stop being a casual compstomping retard and learn to play.
It's been a while since I've played either game competitively, but back in the day I've made it to B on iccup, and sat in Master league in SC2 for multiple seasons with both Protoss and Zerg. So, I feel like I've learned to play pretty decently, but if you want this discussion to have a higher barrier of entry, please let us know what your personal definition of l2p is.
Incidentally, you seem very upset about even fairly innocuous QoL changes like automining (manually directing workers is nothing but an APM sink in BW). Do you actually play the game competitively, on Fish or wherever the current (non)official league resides, that it bothers you so? Automining wouldn't even really affect pro-level games, since those players never really fail at doing it manually. Or are you just butthurt in principle about any kind of change to BW?