What it really is, IMHO, is a call to action for better instrumentation so that the next time one of these things pays us "a visit", we're in a position to find out more about it.
https://en.wikipedia.org/wiki/Large_Synoptic_Survey_Telescop...
I think what you are proposing is having a bunch of large space telescopes around planets. But this might not help very much. All the planets are in the plane of the ecliptic. Interstellar objects are not going to be aligned with the plane of the ecliptic.
The difficulty of putting Hubble or JWST sized telescopes in orbit of other plants is immense. They need constant maintenance as well and will take years to reach their intended targets.
B612/Sentinel has been "in the works" for at least 8 years, but still doesn't have consistent funding. This would be in a Venutian orbit to looks for near Earth objects. https://en.wikipedia.org/wiki/Sentinel_Space_Telescope
IMHO, a more useful location for a space telescope rather than in orbit around another planet would be phased 6 months off of Earth at 1 AU. This would let us continuously observe the "sun side" of space.
It's frustrating because we already have the technology to be able to achieve basic intercepts here, even if they were at high velocity. The only thing in the way is a dilapidated space program.
I think the recent discovery/confirmation that our moon has substantial reserves of water ice emphasizes the difficulties with technology outside of manned exploration. There's a lot of information you can obtain from probes and other forms of remote observation, but it tends to be extremely specialized and very limited. This is not something we should be discovering 40 years after landing on it -- water was confirmed in 2009.
NASA provides regular updates from Curiosity here. [1] What you might find there is that problems are never ending and that progress is very very slow. As an example one of the primary missions of the Curiosity rover was to try to drill into the surface of objects on the planet to start getting some basic idea of what was going on. The problem is that after superficially activating the drill 15 times, it broke. The drill feed mechanism became disabled. The most likely culprit is some dust or other particle caused a critical brake to get stuck. This is a 10 minutes fix for a human on site. For the rover? Countless minds at NASA spent years working out a solution and came up with a solution that is not really sustainable and still leaves major issues with sample collection. That solution, limited though it may be, is as much a testament to the capability of NASA's engineers as it is to the major limitations of probes and rovers. The Planetary Society had a really nice write up on this here [2].
Opportunity recently died after more than 15 years on Mars. An absolutely remarkable achievement for a rover with a planned mission length of 90 days! However, even then it's death may be premature. One of the most likely culprits for its demise is that after a substantial dust storm, which it went into hibernate during, its solar panels were left covered with dust. A Martian janitor with a broom could fix in about 10 seconds, but for a rover - it's time to enter the long sleep. Another side of the story is that during its long life, Opportunity was only able to travel 28 miles, a bit less than 2 miles a year. You end up getting a very limited view of what's going on. Curiosity, for comparison, has managed 12.5 miles of travel in its 6.5 years since landing.
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Finally there is one last major point to be made. We don't know the cost of manned missions. We can speculate on the cost of sending the first man, but I mean once we actually get into the 'normal' phase of putting men on other planets much as we do to e.g. the ISS today. We currently spend about $70 million per person to send them up, and that's a greatly inflated price as we rely on foreign suppliers. But even at that price, sending a man into orbit on a station intercept for $70 million is something that at one time would have been unthinkable.
We will likely see that price drop the single digit millions of dollars, at least in real cost, before the end of this decade. And getting to orbit in space is 90% of the battle. There's an old quote that once you get into orbit you're halfway to anywhere. And that's pretty much true. There will be a serious up front cost for setting up habitation systems but once these are established, I think there's a very strong argument to be made that humans will quickly become cheaper than rovers.
And finally this all completely ignores the human aspect. Putting a man on the moon shaped an entire generation of people with hope, optimism, and a sharp increase in the drive towards scientific pursuits. In a world of needless division, petty diversion, and increasing pessimism towards pretty much everything - you can not overstate how monumental an effect there will be to once again start putting people on other planets.
[1] - https://mars.nasa.gov/msl/mission/mars-rover-curiosity-missi...
[2] - http://www.planetary.org/blogs/emily-lakdawalla/2017/0906-cu...