I'm considering starting a character who's part of the BoS, either based on the Capital Wasteland BoS, or the regular BoS, so will shoot super mutants/ ghouls on sight, take any pre war technology/ books etc even if this involves theft, be very dismissive towards wastelanders, etc. My issue is more that I'll obviously be using Energy Weapons, and normally I play with Melee/ Unarmed. I've read before that an Energy Weapons build is quite tricky to make it work, so would welcome any advice, either on SPECIAL/ Traits/ Tag skills, or on the roleplay as a whole.

Pretty much what my Enclave RP involves

As for stats, they matter little. Whatever SPECIAL you pick will have no impact on the game. Tags should be EW, Science and Repair.
Rush Brotherhood quests obviously, side with Yes Man, destroy the NCR and Legion.

if u like melee weapons get the super slegde or the power fist

How is the EW build tricky?

Any ways, look for Jury Rigging, Meltdown, Laser Commander, and Better Criticals in your build. Math Wrath serves you better IMO than Plasma Spaz. From there, you can pick whatever depending on what you want to play: Laser Gunslinger, Plasma Commando, EW Sniper (What I usually go with, the Guass Rifle is a beast), or the Heavy Weapons Expert (probably hardest for an EW build).

A note on traits: If you really want Wild West, go for it. Just know, you're missing out on one of the best weapons in the game (the unique Gauss Rifle).

For skills, tag whatever you want; you'll have everything damn near maxed out at the end for this to matter. As for skills you'll want to build up, Pistolero nailed it: Science, EWs, and Repair.

Finally, actually obtaining Energy Weapons:

Unlike Fallout 3 and other Fallout games, New Vegas doesn't make you wait to obtain EWs. First, you can get one right where you start the game. From there, go to the Coyote Cave just east of Goodsprings, search every house and building in Nipton, and ransack REPCONN HQ and the Test Site. You'll find that before you even hit Freeside, you'll have a full arsenal of EWs at your disposal.

Thanks for the replies. I thought I'd read before on the forums that someone had said an EW build was quite hard to do correctly, but I guess it'll just be Perception over Agility. Might take Explosives, but I was planning more on a Scribe than a Paladin. I'd thought of taking power fists/ ballistic fists for close up, but this would be Unarmed I think not Melee as suggested above.

Not sure about traits (if any). But SPECIAL as below:

S: 6
P: 6
E: 7
C: 2
I: 8
A: 5
L: 6

Awesome, you get an excuse to pick the Sneering Imperialist perk. Though that perk is close to useless I have a strange fondness for it.

Dont do a BOS play through. DONT. Do an Enclave RP like me

I like it as well, but it's quite useful since majority of humanoid enemies in this game are Raiders which are affected by the perk.