Hi Dave,
(All in 00 please)
I'm gonna go with a loco that has been mentioned a few times already, and one that just completes the branch line scene, yup the little 14xx/48xx, a fully detailed version with a lovely new chassis would get me parting with my cash ( although the airfix model still looks a handsome little loco, i feel a new model would sell well!)
To continue with the branch line theme, a new 43xx or a new tool manor would be most welcomed by myself too, a Dean Goods would be interesting to see too
As you can probably tell i am a Western modeller, but i'm sure they will all appear one day,
Good luck with this venture though Dave, i wish you every success and will hopefully support you one day when the right model comes along that fits in with my layout, by parting with my hard earned cash
All the best
Matt