Payment plan / consumer contract instead of GU's own contract?

Has anyone ever managed to agree on the standard "Consumer Contract for Construction Services - Single-Family Home/Turnkey Construction" designed by the Central Association of the Construction Industry with a general contractor (GU) instead of the often unfavorably worded GU's own contract?

In particular, the payment schedule differs significantly with all GUs I have known so far (e.g., ratio until the shell construction is completed with carpenter work: 40% in the consumer contract, 55% in the GU contract). Also, the issue of completion date, guarantee for completion or compliance with 5% from the first installment for this, or the 5% warranty guarantee are hardly found at all in the GUs' own contracts.

One thinks they have found a locally well-established GU and almost everything would speak in favor of it, and then it could still fail because of the contract. Does one have to accept this and the risk of overpayment, or are there alternatives, especially in the current situation?

especially in the current situation?

Currently, the single-family house segment is still a seller's market; due to lead times, this will hardly change because of Corona. You will simply lack leverage, as the order books of your general contractor are full, as long as they are not a total botcher with the worst reputation. No general or specialized contractor will let themselves be forced into a completely foreign contract. Have you ever tried to negotiate in a payment schedule and warranty bond?

Yes well, he is not. Then from your point of view, the risk of a total failure within the next 12 months is rather low with a reputable general contractor, right?

Compliance with the 5% of the first installment

Isn't that entitled to everyone by law / Building Code?