He is. It's even been parodied in a quote somewhere in FF/FF+. The thing is, MC's modmod is a complete overhaul of many of the mechanics of the game, and as such it has an incredibly long development time.
It isn't
that much of a complete overhaul. I don't intend to change nearly as much as FF does, but my changes are mostly improvement to how things work rather than sprawling additions.
I'm not fully decided about many of my ideas, and implement them differently in versions. I start over fairly often, as my attempts to update to a new version of FfH or FF often don't go well otherwise and sometimes even without merging I end up breaking something and never find out what. I have several versions on my computer, since I haven't taken the time to try to move features I like from a broken version to a working one. Generally I just make minor tweaks to the main mod or FF as I play. It has been quite a while since I really tried modding in earnest, mostly due to being busy with school. Modding stagnated more once I decided that I wanted to use the FF schema/dll as a base, but would have to strip out most the non-vanilla FfH content before really starting. Making a de-moded FF seems rather daunting.
As for Sphener, doesnt the lore say that he's forsaken his status as the Archangel of Junil and therefore lost many of his angelic abilities?
Sphener never was an Archangel. Junil's Archangel is Sabathiel. Sphener was however a true angel (created as an angel rather than processed from a mortal soul) and seems to have had a fairly high rank in Junil's complex hierarchy and an important role in the rituals that take place in Junil's throne room. We know Sphener had a twin with the same rank and abilities, and that before he decided to fall they always mirrored each other to maintain some divine symmetry.
Sphener chose to fall, just as Cassiel and Basium chose before him. I suspect the regulations allowing an angel to fall were written when these two angels refused to abide by their gods' orders, and are rather punitive. The main punishment for falling is loosing their god' ara. An ara is the protection the god provides against the other gods. I suspect it may also mean loosing a connection from which the angel would otherwise have been able to draw a nearly infinite supply of their god's mana. Before the compact 2 gods had withdrawn their ara from their archangels. Aeron was forced to withdraw his from Odio when Odio ignored the ceasefire made in order to allow the negotiations at the Seven Pines. Kilmorph was only able to draw him into a prison of rock once Aeron's ara was removed. Previously Sucellus had withdrawn his ara from Cernunnos when the latter insisted on leaving their peaceful lands and track down his son Gower. Cernunnos felt like his soul had been ripped from him and became quite vulnerabel to depression in Agares vault, but because of his love for his son he was able to land the only successful blow anyone but The One ever landed against Agares even even without an ara. I assume that Sucellus gave him his ara back when he intervened to save his archangel and entered the Godswar. A fallen angel may be weaker, but can still be quite strong.
Falling also makes angels mortal, sort of. They still don't age and are invulnerable to illness, but they can be killed violently (as seen at the end of the Blood of the Angels scenario when Auric murders Cassiel; Cassiel likely had more than enough power to defeat Auric, but would not use the power lest he risk being worshiped as a god, similar to how he refused to use his ability to heal the victims of a plague and so founded the Ordine Medicos instead). Before falling, a violent death could at most banish the angels/demons to their god's vault temporarily to heal. They could probably come back almost instantly, but would be very weak without the time to recover first. Some of Kael's posts (and Aurics words in the scenarios) seem to imply that falling means the god's vault will be closed to the angel/demon, making him unable to heal and thus meaning his death permanent. I prefer to think that a fallen angel is treated the same as a mortal. Instead of going to his god's vault body and soul, the soul alone moves on and needs considerable processing before a new spiritual body can be made. The angel could return to his old god's vault if he remained devoutly loyal to him, the same way a devout mortal would. If not loyal to any god, and former angel would just go to the Netherworld. (I suspect that Basium intends to use this to cheat; as the former archangel of life, he knows several passages he could use to escape from the Netherworld and return to Erebus to keep fighting, even is he has to possess a mortal instead of regenerating his old body.) Most fallen angels have probably betrayed their gods completely, and are more likely to go on to serve their enemies. Sphener fell in order to help Junil keep an oath, so Junil is still quite fond of Sphener and would likely welcome his back. I have a feeling that the Compact may only ever let an angel fall once though, so gods cannot encourage their servants to nominally rebel in order to circumvent the restrictions of the compact.
Sphener can no longer perform miracles on his own, but his memory of his former service likely leaves his the equivalent of an Archmage of Law magic, a high priest of Junil, and an experienced warrior combined. No mortal understand divine law and rituals as well as him, so no one could pray as effectively.
Sphener's evil equivalent Mardero is not a fallen demon, but a cambion conceived specifically to get around the Compact. (In the D&D campagn he was half demon and half angel of Oghma, so that he would be immune to the effects of the mists that made Mammon's invasion force insane amnesiacs.) I suspect that he is the son of Hastur, Lord of Nightmares and Archangel of Mammon, himself. Now that Cernunnos is a god, Hastur is probably the most powerful of all the archangels. It seems that he orchestrated all the acts that almost led Tebryn to destroy the world (including manipulating the most evil and likely most powerful goddess, Ceridwen), purely as a distraction to keep Condatis unable to protect Danalin from his control. His influence over the sleeping Danalin may actually give him more power than any god (as it seems a god's subconscious mind may be stronger than his conscious, and not bound by the compact), but that part of his power probably would not be passed on to his offspring.