Startup as a service where your ideas can be tested, validated, built and grown.
Help with pitch decks and business plans
Help with market expansion/foreign market entry
You can pick and choose the services you need, not necessary to have to purchase all.
Which services would you need the most help with?
No. Because if as an owner I'm not doing these things myself, I'm not learning anything, and I won't be able to manage my business in the future.
That said, your service could be a consultancy instead of a hand-off, and you could help me do these things by teaching me the steps, doing some of the leg-work, and returning the raw information and analysis so I'm getting an education instead of just outsourcing work I should be doing.
Every startup needs to go through those steps, but you have them in the wrong order. The first thing any startup needs is marketing strategy and validation, before product, before a plan, before fundraising. I think you are calling this idea validation, but it's more than just idea validation. Marketing strategy informs what the product should actually be, determines not only the size of the market, but how that audience should be marketed to, and how successful that marketing is likely to be. It helps determine the business model, the pricing model, and the growth path.
While I would hope that those people who come to you for later stage support have done that first part, I would bet real money that most have not done the first part correctly or thoroughly.
My suggestion is that you start your offering as an audit. You will audit what stage of readiness the startup is in, and then you will suggest what steps in what order are needed to lead to desired success. You may have to walk them back to steps they skipped or did poorly. And while you could offer support them in any of the stages you list above, you're not going to have happy clients if you let them proceed when you know they failed in some way with the pre-work that should have been done first.
With my coaching clients, I start with a discussion about what they think they want. Then I dig into what they actually need. They are rarely the same. For example, when someone says "I just need help getting more sales," it is rarely a sales problem. Most often it is a product problem, and fixing the product is what fixes sales.
There are definitely values in the services you mentioned, for both startups and established businesses. I do see Paul’s points below as startups may need more coaching to identify priorities & root causes. Another suggestion for you is to use examples to show potential clients how you helped past clients in each of the service areas, so they get an idea of the expected benefits of your services.
As someone involved with startups and who has been a founder/cofounder i do believe there is a market for products geared towards startups however your concept has too little detail to understand how this would benefit a startup. For example there are many types of startups and they each require a different product. So what types of startups are you focusing on?
Also you seem to be trying to do too much all at once. Maybe you should just start with one simple product or service get traction and then build more from there.