Fortunately my stuff is still the very current Garmin G3X, 912is. I made those purchase at the time of the Kit. Im near completion 2.5 years later. You comment about having lots of time available to a build. You could be done in 1 year and Ive heard people do it in less than that. I am not retired and I am raising two teenagers. Even so, I could have finished this already, even 2 as early as 22 months under those circumstances. So, it sounds like you could consider buying the whole deal at once and avoid possible build delays while waiting months for something to arrive from Austria or someplace.
Eddie