16 planets is suicide unless you take your difficulty 1hw down a lot. You get about 6.5x as many units but deal with 16x as many waves. Try adding 2 to your difficulty with single HW and that's about how many units you deal with to defend against, proportionally.
The 3k knowledge per planet will not allow you to get mk 3 everything, and you have nowhere near enough power and resources to make all the mk1 ships. Just having more bonus ship types adds very very little. Particularly since turrets are better for defense in general anyway, among other things, and there's tens of thousands of knowledge of those. It takes 2.5 planets to get a ship to mk 3. You need to spend much of that knowledge from the HWs to get turrets, since your ship cap:wave amount modifier is much worse than 1HW. By the time you're done, you might have 3 ships to mk 3, some turrets and maybe flagship. Those ships are likely to be triangles or their replacements, not autocannon pods or mirrors, whether you have those ships or not.
It's really, as uberjumper said, faster to win and faster to lose. More punishing of mistakes, but good strategy and tactics gets rewarded more as well.
The AI worlds also do get more reinforcements and such with a multi-hw game and the planets are of significantly higher average tech levels so it's not like you're getting more ships with reckless abandon, but the comparison between human defense and AI offense for more homeworlds is about the same as human offense to AI defense so BOTH sides have the potential to quickly lose.
The current hot problem isn't that the game is going faster. The problem is the planet skipping and bypassing most of the game's depth. Making more than one homeworld suicide just narrows playstyles in the game and does nothing to encourage using more aspects of the game. You'll alienate people who want to play 80 planet maps while taking 40 of them to beat the AI games that last 4 hours for no other reason than to make people who like the game to take 20 hours instead (and can easily just keep it taking 20 hours by selecting 1 hw instead of 8 when setting up the game) happy. It's like removing the ability to play with 10 planets. 10 planet maps net a really quick game too, where you can easily "deepstrike" across the entire map, but I don't see a huge push to remove that feature from the game because you can win a 10 planet map in a blink.
As a comparison to Civilization, it would be like only allowing gargantuan sized maps, and no smaller, because smaller ones make the game end too quickly. You just decrease the potential userbase to only those that feel like playing multi-day games of Civ. This isn't a pvp game. You don't HAVE to have an equivalent time with 1hw as you do with 8hw. You don't HAVE to choose the same difficulty for the AI as everyone else. You aren't LOSING THE GAME if you aren't as good as someone else, or are using different settings. I think everyone is just feeling like they're all losing the game because they can't win the same speed with 1 hw as 8, neglecting the fact that they too can try to win with 8 hws too. Nothing is stopping them.
As a side note, I stopped playing multi-hw for now because it's too dangerous since I can't so easily floor AIP forever to keep defense trivial. I've sort of gone back to school in 1HW.
I say just leave it as it is so those that don't like taking 20 hours to win a game can have faster games without resorting to the shallow game that is 10-20 planet maps.
Edit: OR OR, add a super-blitz game mode where everything does four times the damage over again as blitz, everything costs 1/4 as much to build, takes 1/4 as long to build, 4 times as much armor, waves come four times as often, AI reinforcements come four times as often, ships move double the speed of regular blitz and so on. I'd probably play 1hw mostly with that and be fine. The main reason I multi-hw is because a single hw game usually takes far longer than I'd like. Setting the speed to +10 is too choppy of a workaround and screws up scrolling horribly.
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