Many good ideas and comments here. Due to work, I was not able to check everything and add my own responses last week, I wll try to summarize some points now, or at least, provide some direct answers.
Sorry, but... what??? I stopped reading right there. SV is in my experience the easiest to counter. If you are having trouble stopping an AIs SV, you are not using your spies well, or at all. The AI has a sole SV "strategy": it plays "wide" with its SPs. IN appearance, this is very effective and difficult to counter, but in reality, it's as easy as beating a 2 year old in chess. You need one or two "super spies", promoted to 3rd level with at least one with the Rocketry disruption promotion, and then the right policy cards, and you send those two on permanent vacations in foreign soils...
I don't think they will change the SV. Hopefully though, they will change the AI in its, among many many failures, inability to defend against spies.
Maybe my wording was not correct - it is not it is not easy to counter it (and get the time you need for a different victory). My main gripe is it is a counter in which you cannot recover from failures, so once you start "blocking" a space victory, you know you have to speed up any other victory you are trying to achieve (specially if you are being peaceful).
I have been playing with spies focused in blocking space victory, and I kept AI at bay probably for 100-150 turns (all spies destroying spaceports and factories, except one quartermaster). Main point is, this could be easy with a single AI opponent racing for the victory. It gets more complicated with the limited number of spies , and three-four civs to keep track off. Of course, I was going for a peaceful score victory, so the objective to hit turn 500 complicated things. In that sense, it was just frustrating to see any failure (RNG) in destroying an "active" spaceport was just one "life" less I had. Was even more frustrating when Scytia managed lo launch two components just the turn before the spy destroyed the spaceport.
Of course, I have blocked it via war as well several times (and in this game, after the two Scytian lucky launches, I had to resort to war too… if nuking all Tomyris' spaceports can be considered "war" in a strict sense and not just relentless destruction
), but I find off-puting the combination of (a) having an artificial limitation on the number of resources (spies) you can devote peacefully to stop this victory plus (b) that once a "point" (launch) is scored, there is no way to take it back, forcing you to "race" against the space race.
Compared with cultural victory, you can both increase your culture output, raising the treshold to be achieved, and steal some of the sources of tourism (which has the effect of slowing the enemy and helping you raise the treshold). It might not be more perfect either, but seems more dinamic (in certain sense, can be compared to ending a match at a fixed score, or at a fixed score + x points advantage (e.g. tennis) <- the first is a race for the last point, the second has the increased challenge of outclassing your rival).
In that sense, I consider the option to "lose" some of the space modules you sent would indeed add an additional challenge (and drama) to the space victory, as well as additional strategic layers (rush all launches at risk, or plan for "supply" launches to ensure your already launched modules are well preserved). I do not see it as adding randomness (as the decay of modules can be calculated, and the only actual "random" factor is the success of spies, which is already present). And I think the extended tech tree Will be meaninful for the space victores if adding improvements for stronger modules.
Nevertheless, I see other potential interesting options in the thread, as involving the new resource and power mechanics in the space victory, which may tie in turn with the ecological theme (the launch projects might consume relevant quantities of power, that you need to provide either from fossil sources - risking the environmental consequences -, or by developing new, Green technologies). I do not think they will completely switch the theme of scientific victory to ecology, but it may be relevant for it.
I like as well the considerations to tie in the world congress (not only for scientific victory, but for several others as well, being able to raise some type of emergency focused in blocking a victory: hey, this guy wants to get alone into mars: ¿should we enforce an embargo in its aluminium and power-source imports and maybe dismantle his spaceports?. Hey, this guy is converting everyone to his religión: ¿should we push to reconvert X cities and make it more difficult for him to spread?. Hey, everyone wants to go to this guy's place... ¿should we offer other different venues and demonstrate his tourism spots are not that worthy?....)
