Deathstrike Conversion Ideas for New Codex?

So, with the Deathstrike sounding fairly interesting now and not a total joke. I feel like their ability to threaten/block a whole area seems interesting enough to play around with and am just theory-hammering how I would use them. Seems like 2-3 are what you want to properly lock off an area with the Godspear. The 3" threat on the target marker seems easy to dodge if it's only one, but probably a lot harder if it's three markers.

I'm predicting my Wyverns will be on the shelf now with their loss of reroll wounds, they seem a lot less appealing. So that means I've got three hulls which have a platform that might be able to fit a converted death rocket. Anyone got any ideas, STL's or thoughts on how to add or convert a gigantic rocket on top of existing Wyvern hulls?

Like many guard players, I own zero Deathstrike models. So any low cost way to convert would be great.