The Bane Wolf really is kinda naff honestly as getting close enough to be effective is suicide. The Hellhound has its purpose for reliably and quickly digging enemies out of holes and the Devil Dog is well... a reasonable distraction/all round tank.
I'd make the Leman Russ an Executioner in the current meta as the high strength AP2 in large quantities is invaluable. Don't glue in the sponsons, and I certainly wouldn't use plasma cannon sponsons because they spell a quicker death for your almost Land Raider price tank.
The Manticore is fairly effective, I'd probably keep that. I've had mixed-excellent results with it from time to time.
Taking a Platoon and a Veteran Squad is actually a pretty reasonable way to start out at low points and even up to about 1500, I've been working my Guard that way for years and I still keep a 2:1 win ratio with them. The Platoon can hold objectives and push the front while the Vets take on a certain role by having 3 plasmaguns, flamers or meltaguns, maybe even a doctrine. A word of warning though, if you take them you should consider either a Vendetta or a Chimera as mandatory transportation.
Of course, getting special weapons can be a considerable pain in the rear end. If you play Space Marines and have a decent grasp of conversions then you could use all the excess plasma/melta guns from pretty much any Sternguard/Tactical/Command Squad box but otherwise, I would wholeheartedly and seriously recommend these Forgeworld kits:
http://www.forgeworld.co.uk/Warhammer-40000/Imperial_Guard/Cadian_Shock_Troops/CADIAN_HOSTILE_ENVIRONMENT_TROOPS_MELTA_SQUAD.html
http://www.forgeworld.co.uk/Warhammer-40000/Imperial_Guard/Cadian_Shock_Troops/CADIAN_HOSTILE_ENVIRONMENT_TROOPS_PLASMA_SQUAD.html
Basically, it prevents the need to buy endless amounts of Command Squads for the special weapons alone if you're on a quick and tight budget.