I still disagree. The card has a timing condition (while in play) which would have to happen sequentially, as they don't happen at the same time. And after it's happened, you can't go back to retroactively increase the previous number, from the card you've now resolved.
Still, this might be one for the rules lawyers...
That's a compelling argument. If "while in play" is a point in time (like "when you gain this" is a point in time, and "when you play this" is a point in time, etc), then all those effects trigger simultaneously, which means the player gets to choose the order.
However, is "while in play" a point in time? My understanding was that it was not, that it is a range of time during which the condition holds. For example, while Moat's defensive power occurs at a specific point in time -- whenever it is revealed in response to an attack -- Lighthouse's is just a passive state that you are in whenever it's on the table. There's no point in time where the "while in play" triggers. It's just always active.
Another way to look at it is that Lighthouse's defensive reaction doesn't get ordered with respect to all the other events that might occur during the game. As people take their turns, lots of events are triggering, and you never have to identify a point within that sequence of events when the "while this is in play" part of Lighthouse occurs.
(Lighthouse is maybe not the best example, because after it says "while in play" it then says "when another player plays an attack card" which IS a discrete event. Goons and Haggler operate similarly. But how about Highway and Princess?)
If "while in play" is a passive state, therefore, and not a discrete event, then I would still argue that two active "while this is in play, add 1..." effects would recurse over each other infinitely.