Fast home made salads like Subway are possible with a few different but just as tasty ingredients. Some things to try that you can buy pre-prepared.
You can buy catering bags of ham and salami pre-chopped for pizza making purposes. Freeze in small portion bags suitable for a few days, and take one out of the freezer and put in fridge every few days as required.
Roasted pumpkin and sunflower seeds (substitute for cold cuts).
Anchovies or sardines and Sprouts.
Sun dried tomatoes, some suppliers have pre-chopped (they keep fine in fridge).
You can buy pre-sliced onions, but usually only in 5Kg+ catering sized bags, They do freeze OK.
Many other veges are available pre-chopped and frozen for cooking purposes, many of these will be great in a salad.
If you make the salad in the morning to take to work the frozen parts would keep it fresh for a while, so no need to defrost them. Sort of like an internal, edible ice pack.