Yet another market ?
I am not sure there is a major need for this, in fact this is beyond the core business of a registrar. IMO you have to focus on a clear angle first, and avoid function creep (speaking from an IT point of view).
It's true, you need volume. At $10, after registry and Icann fees, and credit card processing fees your margin will be around $1 a pop. With a few thousand names in your portfolio it can be financially viable but not very profitable. That's why registrars usually sell hosting, SSL certificates, whois privacy and ancillary services.
Now you can run a barebone operation with E-mail support only. Then in theory you could be running a low-cost registrar from your basement in pajamas
If on the other hand you want to offer round the clock customer support, provide a superior experience you'll need to hire staff and this is where the costs start piling up. But I guess that's what call centers are for right.
You may need an accountant, you probably will if your business takes off. You'll have to file taxes.
You will probably need to have a legal counsel on a retainer too, to handle the complaints, the UDRP cases, and the various abuse & DMCA complaints you will be dealing with on a weekly basis.
I have made some financial projections, and I have actual experience with a few ccTLDs. Getting started is not the problem. The real killer is the administrative overhead. Do not underestimate the daily grind.
If you run your own private registrar just to manage your own portfolio there is no big issue really. Because you are only accountable to Icann and the registries - that means paying your fees in time and handling compliance issues if they ever arise.
Dealing with the public at large, even a sophisticated clientele like domainers is of course different.
For me the problem is how you are going to position yourself. I think people have to take sides sometimes. If you are going to serve clients but you compete against them at the same time this is going to cause friction. That's why domainers are not comfortable with DC/HD or other registrars run by domainers. Ever wonder why Uniregistrar for example is not more popular among domainers ? Domainers may have to use companies like DC to catch and bid on drops but it is clearly an arm's-length relationship. I don't think this is what you want.
And I understand that you would be targeting domain investors. They are demanding and not the most loyal customers. They are certainly going to want great pricing. But they have the coupon entitlement mentality, many domainers do not realize that a .com domain name costs more than $8 before you even make a profit.
Even if you stay away from all those silly nTLDs (you have my blessing), your clients will probably want a range of ccTLDs, so they can keep as many names as possible under the same roof for convenience. If you want to be a registrar for many ccTLDs, you will have to repeat the accreditation process again and again, the requirements will be different every time, and the rules are different from one ccTLD to another. Even when they all use the EPP protocol, there are TLD-specific extensions that may need to be implemented properly (a technical discussion
here just to give you a glimpse). And it costs money. It costs money in development work to accommodate extra TLDs. The application process costs money. The ccTLD registries will often require that you maintain a prepaid account with them. So you have to leave money. Obviously you don't go through all this just for a few customers, it's not worth it.
That's why even Icann registrars are often resellers for ccTLDs. They outsource the complexity and the costs they would otherwise have to bear.
Now for the technical part. It can be outsourced. The backend can be quite basic. An EPP toolkit of some sort, you can even write your own scripts. You will want a website of course. It has to interface with the backend and be secure enough. You could use a turnkey solution from Logicboxes but this is not very sexy and not really the road to differentiation you aim for.
If you have the opportunity to go to a domain conference I recommend that you talk with people who work at registrars, you will learn a lot from their experience.
