[Yum] any better solutions for yum based setup?

[pythonic at gmail.com (Shekhar Tiwatne)]

Hi,

I am new to yum and want to solve puzzle below.

Problem: 
I have three yum repos say R1 R2 and R3.
Using yum I want to download rpms pkg1 pkg2 and their respective
dependecies to a sigle directory D1. This to be done every week.
Then yum-arch D1
So others can use point to D1 to install/update
But this should exclude the rpms that are part of min. Fedora install.

Not so good solution:
Copy a min install box's /var/lib/rpm to `pwd`/var/lib/
sudo yum --installroot `pwd` --download-only install pkg1 pkg2

Questions:
Is there any other better method to avoid --installroot and
/var/lib/rpm or atleast /var/lib/rpm ?
     I dont want to others to point their yu.conf directly to R1 R2 or R3
Is this possible without root privilleges(without hacking yum sources)? 

I m using Fedora Core 2 and yum-2.0.7
TIA.