Many thanks for sharing your thoughts Axe and Derek Dansak, I really appreciate it! If anyone else has any ideas please fire away! I think looking at things from a business view and wanting to minimize costs and labour gives a new twist to some of the things we talk about here.
Anyway, regarding storage of prepared sauces I thought that they would probably be fine for up to a week provided no meat touched them while in the fridge. I'm not sure about that aspect, though. I guess I'll need to test it out (and report back here). Another idea would be to freeze some of the prepared sauces.
You are right that we'd be much more versatile with just the BIR approach, of course, but I fear that curries would not be as popular as they are in the UK so we tried to restrict ourselves to two or three that are very different from each other in order to minimize costs (keep in mind, this is more of a bistro/pub sort of thing we had in mind and not a restaurant).
The reason why there's no Korma on our fictional menu is my personal impression that a Korma tastes *similar* to just using "german" curry powder blend on meat. I'm willing to be persuaded that I do need it, though

Vindaloo and Phall are completely out of the question, though. Much too hot for the average german. If someone wants a really hot curry I'll just toss an extra teaspoon of chilli powder into their Madras, I figured.
Axe, you said you always order King Prawn - do you mean as King Prawn Massala or any other curry? We're trying to minimize the different cuts of meat and fish we need, too. Hence why we have only Chicken or King Prawn (actually, me and the wife are not too found of fish and/or prawns ourselves but we know how people love them even if they were frozen and because they cook so quickly).
I'll need to take a closer look (meaning: cook one) at a biryani, I've actually never had one. If the end-result is *considerably* different (taste-wise and looks-wise) from a Madras or CTM then that sounds like a nice candidate.
The veggie choices so far already included a Sag Aloo but I didn't mention it purposely (didn't want to restrict other's thoughts). The "Rajma Masala" you mentioned is an awesome idea (previously unknown to me, too) because we both love kidney beans - do you have a BIR-style recipe you can recommend (or any other)?
I had a look at some "Dal Sambar" images and I fear that it just doesn't have the looks of an appetizing meal (similar to a Tarka Dal). I realize this has nothing to do with taste at all but I think it might be important for people who've never ordered it before and see some "brown stuff" on their neighbor's plate. I want the dishes to look great - and the veggie ones even more so as they are often just tacked onto menus. The indian cuisine has so many excellent veggie dishes that even I could turn veggie. And I want to show that potential. Chana Masala is definitely going on the menu (btw: has anyone tried these MDH packages for Chana Masala? - any good ?)
As for lamb: Lamb is fairly hard to get here in Germany. It's either minced and frozen (what I call "brain mince" due to how it looks once it gets filled into the package) or fresh but then only available from, say, a Turkish butcher. Since you cannot rely on them having fresh lamb available on a constant basis I'd rather not use it all.
Derek - I'm not sure I understood your idea correctly. With "Blended onion" do you mean sort of a base gravy ? If so, then that's actually kind of what I meant to say but a little more broken up then my idea. There are actually a multitude of possibilities for, say, a CTM:
1) Tikka get chucked into pan along with fully-prepared Tikka Massala sauce (including base), heat it, done ? - as outlined in first post
2) Tikka gets chucked into pan with base gravy and separate "masala sauce", add prepared "Tikka Masala" spice mix. Done.
3) Full-on BIR style (separate gravy, masala sauce, separate spices and so on)
When you say cooking the chicken in the sauce I'm guessing you mean the "blended onions"? If so, I guess that'd be my "pre-cooked chicken" right there, correct? That'd be a sound idea.
Any ideas on how any of the members would run such a business that needs to minimize work and costs (but still taste good) are more than welcome. While we did throw together this *hypothetical* menu we do indeed intend to start a food business at some point in the future (say 5-10 years down the road).
If anyone is interested in the menu we came up with please let me know and I'll translate it and post it. We even went as far as classifying where each ingredient would go (fridge, freezer, pantry and so on) and which ingredients would be on our shopping lis (not finished yet, though, missing curry base and sauce ingredients).