is it just me?

[Eden]

Yes - you can stretch the cage a bit. From the photos it really doesn't look like your bottle clearance should be all that bad.... looks like way more space than I have at least (my seat tube mounted bottle just about touches the cables). You may simply need a short bottle rather than a tall one and some practice getting it in and out. My cages are not side entry, but the ones on my race bike are split in the front - so I don't have to pull the bottles straight up to get them out. If your cages force that, you may need to try a different style. I have the plain old fashioned wire ones that come up around the front of the bottle on my Ti bike. Those work fine too.

Seat bag- looks to me like you have a really small saddle with short rails - nothing wrong with that, but it does mean the clip has a hard time fitting (and probably won't fit well, even if you move the saddle.... the rails bend where the clip wants to sit flat). If you want just a little seat bag, I'd suggest a type with velcro attachments - like a Lezyne or Timbuk2 - I have one of these - fits a spare tube, a co2, a small screw driver and tire levers, but not much else.

I've never tried to find full fenders for my 650 bike (wouldn't accommodate them anyway...) but race blades are fine for group rides, as long as you put a nice long, wide buddy flap on the end.