Unless your plot has real drainage problems, I wouldn't suggest anything drastic unless you want to do things like raised beds.
Adding organic matter improves soil structure so will always be a Good Thing.
Not sure about specific crop matters.
However, bear in mind that we had a very hot and dry June in general, and that despite the last two summers, the long-term trend is predicted to be warm wet winters and hotter drier summers (I think).
I'm a bit worried about all these predictions....... If the long, long, long term predictions are as inaccurate as those short long term predictions for this summer then who knows what sort of climate we are going to face in the future? We were told: "a warmer and sunnier summer ahead" and just look at it. Watering can sales have fallen through the floor!
On the plot it is hard to consider too larger changes for the following year as the weather is so unpredictable. I said this year I'd not even bother attempting out-door tomatoes on the plot next year having lost them to blight 3 years running. But - knowing my luck - next year will be warm and not too wet or humid, an ideal tomato growing summer and I won't have planted any!! (so I might just stick in one or two as a bit of insurance)
So... if we make any changes to account for extra wet or dry or hot I think they need to be just little steps within our normal range of veg growing techniques. What we might find is that we have to change the type of veg we grow.... somethings will be more successful than others...so increasing the successful crops and decreasing the problematic ones is probably still the way to go.
A bit of experimenting is the way to learn what works best and then, the following year, trying to remember what conditions were like when you did what it was that worked well...
![wacko :wacko:](https://chat.allotment-garden.org/Smileys/green/wacko.gif)
I find dry hot summers are easier to adjust growing veg to than soaking, chilly grey ones. It's much easier to add more water more often than it is to compensate for too much of it and not enough sun.
Reduce the number of onions grown and harvest a bit earlier when the sun shines rather than waiting for wet mid July when they are usually ready...??