Is it possible to re-partition internal memory for just sdcard in place?

So I have been playing around with my android tablet and I have come to the realization I know just enough about what I am doing to be extremely dangerous, so I figured I should stop and get confirmation the path I am going down is sound

I (like many others) are running into internal memory issues and I am looking for a solution

My device has 500M of currently allocated to "internal memory" and 5G of internal NAND mounted to be the sdcard

results of df

df
Filesystem             Size   Used   Free   Blksize
/dev                  438.3M  36.0K  438.3M   4096
/mnt/asec             438.3M  0.0 K  438.3M   4096
/mnt/obb              438.3M  0.0 K  438.3M   4096
/system               1023.0M  365.6M  657.4M   1024
/data                 503.9M  408.3M  95.7M   4096
/cache                503.9M  8.5 M  495.4M   4096
/mnt/sdcard           5.0 G  324.4M  4.7 G   8192
/mnt/secure/asec      5.0 G  324.4M  4.7 G   8192

All of this is internal memory, there is no external SD card installed. What my question is, is can I re-partition what is currently mounted as the sdcard into two partitions, one say 3G fat partition to continue to be my sdcard and another 2G ext partition

I'm not so crazy as to try and re-allocate the sdcard memory back to /data - I'd like to do all of this in place and not have to re-install anything (apart from the apps that I want to live on the "sdcard" of internal memory)

What I am trying to do is the internal memory equivalent of the two partitions on an external sdcard to use with link2sd

So question is, is it worth going down this road, or should I just stop now?

If the answer is, yes, it's do-able, then this is really where the "just enough knowledge to be dangerous" comes in...

looking at /etc/vold.fstab I got the following:

dev_mount flash /mnt/sdcard auto /devices/virtual/mtd/mtd9/mtdblock9
dev_mount sdcard /mnt/external_sd auto /devices/platform/rk29_sdmmc.0/mmc_host/mmc0
dev_mount udisk /mnt/usb_storage auto /devices/platform/usb20_host/usb /devices/platform/usb20_otg/usb

which I am assuming means /mnt/sdcard is coming from mtdblock9. The fact that this looks like a virtual device is what has me stumped. I don't really know where to go from here to get the equivalent of two partitions on an external sd via re-partitioning the internal memory

what are my next steps?