Okay, I used to endulge in Shadowrun back during its Second Edition, and left after the start of the Third. I finally decided to try the Fourth Edition, and so far I'm pleased with my purchase. And then I was directed to this forum, so I'm happy to find like-minded folks.

Of course, now that I'm interested in Shadowrun again, I'm starting to wonder how to graft all sorts of other stuff into it. Like battlesuits, small mecha and robots, demons and other foul spirits, lovecraftian creatures, and of course, furries (I'm a furry and unashamed to admit it).

For the beast-folk, I'm torn between a modified form of Shapeshifters, genetically-engineered lifeforms, people getting genetic, surgical and cybernetic modifications to resemble beast-people, or a mix of all of the above.

Any opinions on this?

Furries were probably officially introduced in the Year of the Comet, when the SURGE phenomenon happened. Read about it at the dumpshock wiki here:
http://wiki.dumpshock.com/index.php/SURGE

Basically, the increased ambient magic level produced a variety of oddities (including natural orichalcum deposits which triggered an orichalcum rush), which included a bunch of people expressing as cyclops, cat girls, and all sorts of fun things. A lot of Dumpshock folks don't like SURGE, but it's canon, and it's in the game. More importantly, it may align with your interests.

Any Military Grade armor in Arsenal counts as a battlesuit, pretty much. You are a walking tank when you have one of those equipped. They can have a variety of enhancements common to post-human/trans-human anime.

Small mecha have taken a turn away from humanoid looks due to feedback from the Renraku Arcology tragedy, but you can find some humanoid walkers in Arsenal. They are more utilitarian than "ED-209 Guard Robots" patrolling the streets, serving more mundane roles like bartenders and house servants (and of course, black ops ninja assassins if you want to play up the expensive ridiculous angle... Arsenal, again, has a couple examples of those).

Demons are simply spirit manifestations that match a religion's theme. You can also play-up the arrival of Shedim, malevolent spirits that possess dead bodies or bodies of mages that are astrally projecting. Or go with the Insect Spirit angle (certainly, an Insect Shaman is striking a Faustian bargain when courting an Insect Hive Queen). Lovecraftian creatures, though, are more likely to be a metaplanar (read: Not Earth) denizen, although you can easily run a Cthulhu-like game using the Horrors from Earthdawn as an interpretation (not canon anymore, but it's easy to maintain the link to Earthdawn).

Thanks for the suggestions. Looks like SURGE is exactly what I was looking for.