So batch payments seem to be the way to go. However, this creates some questions to which some may already have found an answer:
A business plan is - of course - always very optimistic... so I have started with some few clients. They will get some Satoshi on your wallet address every week. There will be a minimum amount before you can withdraw this.
If there are only 5000 clients, this shouldn't be a problem. But what if there would be a million clients - in this case, I assume, it would make sense to use multiple wallets - not only for security reasons, but also for not cloaking the network with one huge transaction. Or do I get this wrong?
Large transactions take a long time to verify and propagate, so there is a point where you should use multiple batch payments instead of one gigantic one.
Another question is: Has anybody experience how many clients would be ideal to include in one batch payment? Is it more depending on the amount of the payments or the number of payments in the batch?
It is entirely dependent on the number of payments you make in a transaction, not the amount. The only time the amount matters is if you have an output that is below the dust threshold.