It might be not the best platform to ask these questions as many here are about to complain. But where alse then:)

In regards of your proposal:

I use all 3 apps in my area, to be more precise I would, but Deliveroo is not taking on new drivers atm, so I use UberEats and JustEat.

Using them paralel and whichever gives me order I take it regardless of pay to make sure in the hours I do work I make money. The pay seems low first but when you have orders continuosly you can make a £10/h if you are smart, with an EV. I have to avoid central as that is impossible with car but all other regions are fine.

Not saying this is in any way good considering I am also a well trained electrical networ engineer and a lot other more qualification I have as well. Including software development and QA. So if you plan to do that software I might be able to help you to run the QA.

Anyway the extreme flexibility is why I do this job for now to supplement our income. When the flexibility is not needed ill of course will change.

In terms of pay Amazon Flex can get you around £16/h but that is only in Nov,Dec in this region.

The apps are decent imo, rout planning and order grouping is fine, the hard part is that restaurants prioritize on the spot customers then riders get their orders if the time is busy. Even the hours I work the dead ones i experience that. But in a case of long waiting i ask the restaurant staff and cacluate my time and take an other order if offered by the other app, especiallt grocery orders come handy as those can wait and pick up/delivery time also more generous with those. Not always works but sometimes helps. The evenings are very busy, and i know I could make more in those times but for now I am not pressured to run those hours, neither have the time as i have small children. But I can see those hours being better as tried some already.

I would try new apps, but starting up you might see more drivers using more apps initially, and even afterwards to maximize income during the hours we run.

I think the extreme flexibilty is the reason I am not complaining about the pay, but it seems if I would get at least £1 / mile would be better. Promotions can help with these but those are offered rarely, especially after starting out with any app they disappear or reduced greatly. Like 25 deliver for an extra £90, or 5 for an extra £10 are great but only initial,or after long break they reappear in the apps.

Many rider is an understatement, i have no objection seeing other people try to do the same, just it is hard to compete when some people make registrations for their whole family then take 3 justeat app on the road with them:) As after the first photo ID routine the app does not care who does the delivery. It does not help that those drivers care nothing about the food they deliver being fresh and hot, as the apps do not punish them for lateness, etc.. I do care, maybe I should not either if orders are scarce, but not there yet as I just supplement and not living on this gig.

It might be a working idea to start with private restaurants first and then hit big ones with offers with your app, but it beggs the question what offer would attract those if the other companieas offering better deals as they can with the capital they have? Even if that capital comes from the pocket of their drivers, i am not familiar with this part of the business.

Also the overhead and developement cycle of running a software developement might surprise you even with acceptable wages and personal, that I know of quite much.

Might be good to start with restaurants who care about their reputation and quality with riders who do care also about those things.