I totally understand fielding what you've got, but this is how we plan for what we're going for also.
I started out with trukks. I do like them, they just get popped, and also don't deliver the size of squads necessary to deal with.....
SW and
CSM for example, because they have pistols and
CCW along with their bolters(so 2
CC attacks) and counterattack on the
SW.
I've seem some guys(and it's on my own to do list)to convert koptas into rokkit buggies. remove the blades and the arm, the skids too, and add 4 wheels. There you go
I play Budgethammer
40k, and in friendly games I proxy where I don't have the official model. Many of us have to in order to try new units without spending 30-150 bucks just to try the unit out.
I'd be tempted to drop a few deffkoptas for more meganobz though. You've got 10 meganbz worth of koptas

They look great, and you want to hum "Ride of the Valkyries" when you field all those koptas, but they don't quite pay for themselves, unfortunately. I've seen 10 fielded to use up points.
Either way I like the theme, and particularly the Grotsnik idea for the
CB. I despise the
GK Codex, and while I won't quite call cheese...just.....yuck. All power weapons.....they will be your nightmare and steal the thunder out from under you.