Modern Vespa

Yeah I would probably use the Packir bags because I have bought from them before and they are good quality. Their 20" x 20" x 20" PK-140Z bag should be large enough for most pizza boxes. I'll look into that

If you look at some of the ways scooter cannonballers have strengthened the rear rack to carry spare gas, you can get some ideas as to how to reinforce it to take extra weight.
Personally, I would try to buy something like a Kymco Agility 125 and use that as the delivery bike. You're going to be hard pressed to find something as reliable and cheap to operate. And at the speeds you are going to travel, Chinese moped tires will last longer, and be cheaper, than anything you would put on a personal scooter.

The Rattler 200i looks like it has a huge deck for a drink cooler but needs the grab rail swapped out for a top box.

I've sometimes considered getting a 2nd hand 150 vespa for the same reasons (since I left my professional work). why a vespa, cause I'm very familiar with them and could look after it myself etc.

Yes, but the Agility is about $2100 brand new. Same engine, except for the displacement. And at that price, you won't care what it looks like after a few months. I would be leery about trying to run one of the 170cc gy6 motors for a business. They took out a lot of metal to get that piston in. When you do wear out the 125, it's easy to punch it up to a 150, or you can put the same top end on it as the Rattler 170.

Purpose built Delivery scooters usually have a side stand on both sides of the scooter. So make sure that whatever you use has at least one side stand, with a large foot.
I think you can get a right side stand for the Agility, because they make a delivery version, and possibly the Piaggio Liberty. I had a TGB Express Delivery scooter for a while and it was a blast to own.

That's a good price.

When I was working for KYMCO we were selling the People S125 for about $2200 and that was over a decade ago.

The Agility might be made in China rather than Taiwan, as some of their cheaper vehicles tend to be. Fit and finish weren't as good on the China models on things like seat stitching, etc. but I believe the motors were equally as solid.

the agility 125's are butt ugly, slow but solid as a tank! the parts are dirt cheap, and they're cake to work on. the original duro tires seem to last FOREVER.

the headlight bulbs burn out at a maddening rate and that's literally the only quibble I can think of.

that would be my 1st choice, second choice would be a clapped out ET4 or LX150. I would probably try and find a roached out LXV seat and adios the pillion pad and attach a small compartment box there. with the addition of front and rear racks you could haul a reasonable amount.

either way I would only attempt door dash or post mates and leave instacart alone due to the possibility of a unwieldy order.

The only thing holding my earning back is Door Dash doesn't show what the items are until I accept the order, only number of items. Dashers are only allowed a limited amount of unassigned orders. I don't do 3rd party apps for those who do or tell me I should.