That’s a nice idea. I’m going to map my thoughts since I might try it too. The ideal kit may differ by age, sex, area, climate and degree of homelessness. Ideal items are cheap, light, useful and easily available (say at dollar stores). Basic needs are security, comfort, food and drink, pleasure and work. Alcohol based products (hand washing liquid, cologne) can be misused.
Security: whistle, flashlight, lock
Comfort: waterproof poncho, blanket, inflatable pillow, puffer coat with hood, socks, footwear, winter clothing, rain gear, camping (cheap sleeping bag, tent) stuff
More comfort: aerosol deodorant, tooth care, hygiene products, small amount anti inflammatory, moisturizer, suntan lotion, lip balm, basic cosmetics, insect bite care
Food: plastic plate, mug, cutlery. High density food - bars, nuts, fruit, cheese. Fast food or coffee shop certificates probably a nice idea. Something tasty as a treat. Powdered drink mix?
Pleasure: pen, paper, cheap music (MP3?), flowers (for women), playing cards, games, art supplies?
Work: help with signs?, odd jobs? Referral to local shelters and services?
Other stuff: dollar store toolkit or sewing kit, blister care, condoms?, mirror, scissors, dollar store Swiss Army knife?, hand wipes
Container: large waterproof bag, duffel, bucket? Mexican markets sell cool, colourful, cheap, large, light durable fabric bags which would be perfect - unsure of local equivalents.