I'm not quite following you. It doesn't happen too often right now cause as you say, you need a bunch of variables:
1) first to go
2) enemy worm on bottom
3) within reach of your own worm
4) crate within reach of your own worm
5) plop-weapon in crate
6) a safe retreat
7) more skill than doubletime
If you already start out with nades/zooks you can skip variable 4&5, making the odds quite a bit worse.
skipping 4 is not so much of a bad thing as it is a choice for the player. Choices are a good thing. You can ignore a crate to get a kill, but if that crate had a SD weapon and you ropponent gets it then maybe he's the one getting the best of it.
that's 1/6 of what you consider a total of 50% meaning regular team17 has a 42% chance of plopping on first turn.
All I'm saying is that a difference of 8% is not really the problem.
The only fix t17 needs is brining back worm select, which were only removed from the scheme by MISTAKE. It wasn't intentional and had no reasoning behind. It still shocks me how even to this day, people just live with it and dare defend the current t17 scheme as it was balanced. Heard the news? It's not balanced, it's random set of rules. What happened is you managed to craft a gamestyle and a set of strategies that became quickly universal and a habit by all players.
This allowed bad team17 players to abuse certain gimmicks that required no thought nor skill and that were effective most of the time. Girder abuse. Why were worm selects there? For that exactly, amongst adding a thousand more situation and strategies for SD other than climb up, wait, use SS.
Seriously, the history with the scheme and its group of players never ceases to amuse me, it's as if a bunch of otherwise intelligent people decided to take something for granted, without questioning one bit of it, and now defend it as if it was theirs.
But hey, it's not like dictionaries don't allow consideration of additions based ona bunch of people using the language wrong - it's called being practical (or lazy), if you have one worm vs 2 in SD, I guess it's much simpler to follow a patern that keeps your winning chances somewhat safe. Obviously, that one SD loving worm with turn advantage is happy following somewhat a constant set of strategies, as opposed as having to defend to select worm which coupled with things like shotguns, petrols, moles or whatever can make it a twice as complicate for the guy who has half the worms.
You see how that makes complete sense right?