I think megaramp as an archetype is not great for a cube's health. However, I do like to shift it from pure green to something that relies on cards like Gilded Lotus and Worn Powerstone. It's more archetype-like that way as opposed to just putting dorks together.
IMO mega-ramp is what necessarily has to play things like Worn Powerstone, Gilded Lotus, Thran Dynamo etc., since (in my understanding) it is a deck that ramps higher than 8-mana (I guess, it's also often called super-ramp). It's uneasy to support, indeed can be not very healthy in cubes, and needs some cheat cards to be present in the environment. That's not what I'm trying to support in my cube. I guess, my desired category of ramp could be called "medium-ramp" (ideally casting 6-8 cmc creatures on t4-t5). I also think relying on dorks is more healthy than on big-mana artifacts because dorks can be played in literally any green deck (alongside with smaller artifact ramp like signets/talismans/other 2-cmc rocks), and are more interactive (you can bolt the bird/bounce the bird). To get some big mana generators we could take Rofellos, Llanowar Emissary and Gaea's Cradle, but that's, perhaps, not really necessary for everyone.
Bigger mana rocks, however, seem to be only useful in Wildfire/Upheaval-type decks (which I do not support) or control lists having several X-spells as their finishers. Correct me if I'm wrong, I haven't had much experience with big rocks (I cut both Powerstone and Gilded Lotus soon after adding them). The only exception I would make is Coalition Relic because it's a fantastic piece of fixing wanted by every non-aggro deck in my list.
EDIT (didn't notice the feedback on aggro creatures at once):
But they ensure the critical mass of 2- and 3-drops in my Red/x Aggro decks, give those decks powerful tools, have immediate board impact thanks to ETB triggers/haste and sometimes can be sacrificed to something like a Carrion Feeder at EOT before they die to their own text. And I didn't really get your point about giving advantage to the fun dynamic. You mean those creatures are just burn spells rather than something more interesting? Well, I think they're a bit more fun than smiple Lightning Strike's because they can be blocked, so you can't just always send them to the face whenever you want. But anyways, I admit there can be more interesting cards. What replacements would you suggest for these three at my power level? Preferably pre-XLN.I just think they are pretty unnecessary. At the end of the day, they are just damage to the face aren't they? They don't really help any particular archetype or deck, they are just very good Lava Axes. I think you can put those cards to better use.
For example, I could run those cards in my Izzet decks. I was tempted because 8 to the face sounds very, very good. But it feels a raw concession to sheer damage more than a fun dynamic.