Hey, got some odd numbers for you related to increasing/splitting damage dice, that go outside the 'norm', or your limits. And strange thing is, even when outside those limits like this, the prices still can't be changed for a specific number of dice (4d4 cannot get more or less expensive). You don't have to update your tables, I just thought this was cool. I mean, compare the numbers I came up with, for the values that are also on your table, with the values on your table. Their the same, except that the route to get there was radically different!
I mean, I came up with 8d2, for 7.5 slots, increased it to 8d4, for a total of 15.5 slots - which is the number of slots 8d4 had if you DON'T use d2s. Increasing up to d20s and then splitting down to d10s also yielded the same costs as the d10s normally had.
Weird.... But awesome.

Spoiler
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Unusual Damage Dice
A d4 may be split into two d2s. Increasing from d2s yields d4s. The total costs resulting from doing this more than once do not change!
{table=head]Base Damage Die|Previous damage Die|Slot Cost|Total Cost
2d2|1d4|0.5|0.5
2d4|2d2|2|2.5
4d2|2d4|0.5|3
4d4|4d2|4|7
8d2|4d4|.5|7.5
8d4|8d2|8|15.5
16d2|8d4|.5|16
16d4|16d2|16|32
32d2|16d4|.5|32.5[/table]
While no d14s, d16s, or d18s exist, in theory it should be able to increase through these and up to d20! Splitting can happen at d16 and d20, to d8 and d10 respectively. Simply put, splitting can happen when the result would be an even number, and increasing increases by increments of 2. There is no theoretical limit, and only what dice you actually have limit you IRL.
{table=head]Base Damage Die|Previous damage Die|Slot Cost|Total Cost
1d14|1d12|1|5
1d16|1d14|1|6
2d8|1d16|0.5|6.5
1d18|1d16|1|7
1d20|1d18|1|8
2d10|1d20|0.5|8.5
2d14|2d12|2|12.5
2d16|2d14|2|14.5
4d8|2d16|0.5|15
2d18|2d16|2|16.5
2d20|2d18|2|18.5
4d10|2d20|0.5|19
...|...|...|...
4d16|4d14|4|31
8d8|4d16|.5|31.5
16d4|8d8|.5|32
32d2|16d4|.5|32.5
...|...|...|...
4d20|4d18|4|39
1d80|1d78|1|38
2d40|1d80|.5|38.5
4d20|2d40|.5|39
...|...|...|...
1d100|1d98|1|48[/table]


As for the current armor deal, do you have armor spikes yet?
What about... Hmm, I'm coming up with nothing... Hmm. Most of the ideas I can think of would be magic armors. *Shrug* Sorry?