What do you think TA is besides a set of tools? If you want a "blueprint" (by which I presume you mean a trading plan), then go to the Strategy Design forum, not the Technical Analysis forum.
The point of TA is to transform financial time-series data into forms that indicate some specific action should be taken. This generally suggests the blueprint to use all by itself, going far beyond your house building analogy. But that doesn't change the fact that a great deal of TA is subjective and thus giving rise to multiple interpretations (aka multiple blueprints).
Right, the technical patterns/indicators/price levels are tools and materials. They are not, however, the analyses that lead to a blueprint. The technical + the analysis = the blueprint for what "works".
The TA bashers here keep re-iterating commentary about candlesticks and patterns and indicators not working. Of course not! If a particular pattern or price bar or indicator ensured that if we buy or sell we'll make money, there'd be no market.
Objective analysis is possible once the particulars are defined.
I agree completely that at any point in time there can be multiple interpretations of which direction price is
more likely to go between now and some future point in time, because everyone has different time horizons, different levels of risk/reward, different reasons for putting on trades (speculating, hedging). There can be a blueprint for a house, a plan for the landscaping, a master plan for the housing community, and so on.
Subjective trading can work just fine for some people. I'm just not one of those people. When I have stats to tell me what's more likely in a precisely defined environment, I'm less likely to micro-manage trades based on subjective concepts like "too high", "feels weak", "due for a winner", and "God, just help me get back to even and I swear I'll never move my stop that far away again".
This doesn't mean I feel comfortable with a lot of my trades. Often times I fall into a zone where a part of me is feeding me all sorts of interpretations of why I should skip this trade, and I hear my voice say out loud, "I'm supposed to place an order here" and then I simply do it. When that happens I found that it's best for me to then walk away for a few minutes so I don't pull the order.