I like it. It's definitely more Magic-ese than the "if you do" version, but the rules implications are much simpler. No more targeting a creature and then choosing not to sacrifice anything.

Seems needlessly complicated, but I'll take more options for interaction.

I think I like it. You can still sacrifice something even without legal targets this way. Thankfully, the wording is simple and easily spotted (when you do as opposed to if you do). Only problem is that players who get too used to this will be more likely to make a mistake using older cards that don't share this template, though the situations where that will be important are few and far between.

I'm sad it doesn't interact with Willbreaker like Throwing Knife did, but I can agree that this is probably better in the long run (especially if it starts getting used more often). More intuitive for players than the "if you do" template. Although that will still have its proper uses (most likely with spells and/or activated abilities, definitely with optional replacement abilities).

Interesting. I hadn't even noticed the "when". This new template is probably more in line with how players expect it to work (though the template is very Magicese). It also gives a lot more control to the opponent: they know how damage is coming when choosing how to respond, and if they do something to save their creature, the Manticore's controller is still down a creature.

yeah, which makes sense given that that's how things like fling have always worked. it basically gives an additional cost to a triggered ability, and that seems reasonable.

I generally agree that it's uglier this way, but I think it's a small difference and the gameplay is worth it.

As demonstrated by Willbreaker & Throwing Knife. That does not read as a combo.

When this manticore ETBs can I use it to crew a vehicle and then throw that vehicle with the ETB trigger?

I think it works, but I'm not sure...

Yes, that works.