Mostly good fun - I've gone this way myself at times
Well open Sicillians and not the wing gambit! (ugh.).
A few more bits to complete a bit:
1 Nf3 Nf6 2 c4 e6 3 Nc3 b6 4 e4 Bb7 5 Bd3!? - great fun and a bit of (old!) theory.
1 Nf3 g6 2 c4 Nf6 3 Nc3 d5 4 cd Nxd5 5 e4!? ^ Nxc3 6 bc and then development before a slightly delayed d4.
Much more popular to go d4 directly there, but there are Ba3 ideas which a few have tried. I was actually wondering about trying Be2/o-o/Rb1 and then d4 to get a Rb1 exchange without dropping a2. Its not obviously silly. There are also of course the Qa4+ antis which seem popular.
The KID/Moderns I suspect you'll just have to go d4 and turn anti theoretical from there. Or perhaps the (very) early Q - side expansion ideas.
I really do conceptually like the 3 b4/e3 lines after 2 c4 d4, but I'm just not sure if they actually work all that well. They'll at least need checking. Some
very random stuff with an early c5 I suppose.
As for the symmetrical, the thematically center oriented/activity thing to do is go for a quick d4. Probably with 3 Nc3 first because the 3.. d5 4 cd Nxd5 5 e4!? variation fits so well! 6 a3 anti benoni say.
Oh and I hate the idea of the wing gambit, but there you go