Hmmm, I've always liked the look of trellis framed bikes:
Sexy and functional.
I've actually always had a fondness for the Spondon frames as well. Just a super cool looking 80's style custom:
that's a cbx1000, but I'm sure you get the idea.
I'm kind of stuck with a "cradle" style frame though, as that is how the engine cases are designed to be loaded. So it woudl be a "hybrid" trellis at best. I wouldn't trust the OEM engine mounts to "hang" the engine as a stressed member It's just not designed to be stressed that way. Not to mention, without a head mount, the engine woudl be too free to "jink around" under loading.
It's been a while since I last built a frame, but it's not that hard. It's just time consuming with making the jigs, getting good tig penetration, etc. Not to mention there woudl need to be several parts machined from billet (swingarm pivot plates, steering stem, etc). Heck, I don't even have a frame table anymore, so I'd have to build that as well.
I'm tying with the thought of making in aluminum, but I'm not sure I want to go through that extra cost or fabrication. Would sure shave several pounds off the bike though.
Ah, daydreaming.....always fun!
And sometimes, it leads to new and/or innovative ideas. It's one of the reasons I always encouraged brainstorming and "out of the box" ideas at work. It's a lot of the reason why my unit lead the way on so many missions. Always encourage creativity, in any of it's forms. Daydreaming or otherwise.