[@vancexentan]
Alright, here I am back again. I'm relatively sure I want to go with Jekyll & Hyde now. 

Specifically the assassin version, still, as hyde is suggested to be able to a quite respectable level of strength, while not being quite so off his rocker as he'd be as a proper berserker... Still definitely insane and erratic, but I think (hope) I can make it work.

Full character sheet soon, in the meantime, have the servant's

[hider=Servant]
[u][b]Servant Character sheet:[/b][/u]
[url]http://typemoon.wikia.com/wiki/Assassin_(Fate/Grand_Order_-_Dr._Jekyll)[/url]

[b]Class Name:[/b] Assassin

[b]Nicknames:[/b] None.

[b]Alignment:[/b] Lawful Good (Jekyll) / Chaotic Evil (Hyde)

[b]Servant of:[/b] To be added.

[b]Weapon(s):[/b] A knife

[b]Wish:[/b] Unstated.
(dr. Jekyll had a small breakdown when questioned on this topic)

[hider=Abilities]
[u][b]Abilities:[/b][/u] 
http://typemoon.wikia.com/wiki/Skill
[b]Skills:[/b]
Powerless Shell (Jekyll) - A
[i]Powerless Shell (無力の殻, Muryoku no Kara?) is a Skill that makes the user difficult to perceive as a Servant, declining one's parameters and suppresses one's Skills.[/i]

Voice of Panic (Hyde) - A
[i]Voice of Panic (恐慌の声, Kyōkō no Koe?) is a mental attack that weakens the hearts of those who hears it.[/i]

Monstrous Strength (Hyde) - B
[i]Monstrous Strength (怪力, Kairiki?) is a Skill that temporarily grants a rank-up to one's Strength parameter for a time limit determined by the ranking of this Skill. This Skill is borne from the holder's nature as a monster or Demonic Beast.[/i]

Self-Modification (Hyde) - D
[i]Self-Modification (自己改造, Jiko Kaizō?) is the aptitude to remold one's own body or merge one's own flesh with body parts of others. The higher the ranking in this Skill, the further away one is from being a proper hero.[/i]

[u][b]Class Abilities:[/b][/u]
Presence Concealment (Jekyll) - A
[i]Presence Concealment (気配遮断, Kehai Shadan?) is the capacity to hide one's presence as a Servant. It is a common Class Skill of the Assassin class.[/i]

Mad Enhancement (Hyde) - A
[i]Mad Enhancement (狂化, Kyōka?) is the Class Skill that characterizes a Berserker, raising basic parameters and strengthens one's physical abilities in exchange of hindering mental capacities and/or in exchange for their sense of reason.[1][29] In some cases, it also affects and/or seals away some techniques, Personal Skills and Noble Phantasms.[/i]
[/hider]
[hider=Parameters]
[b]Base Parameters:[/b] 
Strength (筋力, Kinryoku?) - c+ / B+
Endurance (耐久, Taikyū?) - E / B+
Agility (敏捷, Binshō?) - A+ / B+
Magical Power (魔力, Maryoku?) - E / D
Good luck (幸運, Kōun?) - C / D
Noble Phantasm (宝具, Hōgu?) - C / C
[/hider]
[hider=Noble Phantasm]
[u][b]Noble Phantasm:[/b][/u] ([url]http://typemoon.wikia.com/wiki/Dangerous_Game[/url])
Name: Dangerous Game, the secret game of sin
Quote: "I have no choice but to drink...! ...yes. YES! THAT'S IT!!"
Rank: C
Type: Anti-Unit (Self)
Range: -
Description:
[url=http://typemoon.wikia.com/wiki/Dangerous_Game]an elixir (miracle drug) that allows for the transformation of Jekyll into Hyde, the second personality inside the former's body that claimed so many victims in his life. It can also be used to revert the transformation, transforming Hyde back into Jekyll.[/url]
[/hider]
[hider=True Name]
dr. Henry Jekyll & mr. Edward Hyde
[/hider]
[b]Appearance:[/b]
[img]https://pm1.narvii.com/6687/a214906ccc7f9804d6a478a244c420878ac574c7_hq.jpg[/img]
[/hider]