Your asking reasonable questions, and none of them sound “out there”. Looking at vehicle access, storage, disposal timing, weather, flooding, and what happened to property after a move are all standard lines of thinking in a case like this. In a disappearance where the known timeline is thin and the environmental conditions matter so much, those details could absolutely be important.
The garage vehicle question is especially fair. If a car was accessible, people are naturally going to wonder whether it was searched thoroughly and, if so, when and how. The same goes for the broken down vehicle. Even if it couldn't be driven at the time, what happened to it later could matter a lot. If it was sold, junked, towed, repaired, or moved out of state, that'd be the kind of follow-up that could either eliminate a theory or make it more important.
Your point about the river and flooding also makes sense. Water changes recovery possibilities dramatically, and flood conditions can make it a bigger area where evidence or remains could end up. That is not wild speculation, that is just pointing out how the environment can affect a case.
I also think you make a strong point that investigators should not only focus on the exact day Rachel vanished, but also the weeks and months before. In many cases, the lead-up tells you more than the disappearance itself. Prior behavior, household relationships, access to vehicles, statements made over time, and any changes right after the disappearance can all matter.
At the same time, it is worth being careful about stating theories as facts. There is a difference between saying “this should be checked” and saying “this is what happened.” Your post stays on the right side of that by framing these as questions grounded in facts at the time.
Overall, I think your comment adds something useful to the discussion. Cold cases do need people willing to look at overlooked angles, and asking whether all the avenues were fully examined is part of that. The key is keeping the discussion focused on real questions, documented timelines, and evidence that may still be re-examined.