I'm in my 50's.... so I've been around a long time & worked on almost everything concievable type of project over the past 20 years. Unusual project types are not a problem. I had a trade background until my late 20's, so buildability is not an issue. The only choice to make is how much you want me to do and how much control of your project you want me to assume. I can provide full Architectural services or just design advice, or what most people want.... which is a set of Budget plans to build or renovate their dream home or extension.
An Architect is a fully trained professional, trained in design and documentation. The worh "Architect" is protected by law. Only after studying a relevant degree in Architecture plus achieving pre-requisite work experience can an individual ask to sit the formal exam which will qualify them and allow them to use the word "Architect" after their name. Do not be fooled by terms like "Building Designer", Draftsman, or even "Architectural Graduate". None of these indicates the same level of professional qualification has been achieved. It commonly takes around 10 years to become an Architect.
An Architect can advise you on the best way to proceed with your project, and then produce your own set of custom plans designed to suit your lifestyle and budget.
Why do you need your own set of plans rather than just letting the builder produce them for you? The main reason is that the plans will be better thought through and you will be getting exactly what you want. An Architectural set of drawings is usually much more highly detailed and specific than those produced by a builder. Having your own plans also means you can shop around between builders. Without your own plans you really are not comparing "Apples with Apples". If a builder produces a set of drawings for you there will often be "grey areas" in the design. This allows them flexibility in exactly what they produce for you and so you may not get exactly what you were expecting, or more commonly will just end up paying more to get what you want. Having your own plans means the builders are pricing the same items and so you can get a true price comparison. This means you can put your plans out for tender and decide who you want to use.