I tried doing some searching, but I couldn't find a clear answer.
I'm playing Pathfinder Society and would like to eventually buy Celestial Armor.
My purchase and upgrade plan is as follows, as accumulated fame and gold will allow:
1. Buy mithral chainmail (4150 gp)
2. Upgrade mithral chainmail to +1 (+1000 gp, bringing total cost to 5150 gp)
3. Upgrade mithral chainmail +1 to +2 (+3000 gp, bringing total cost to 8150 gp)
4. Upgrade mithral chainmail +2 to +3 (+5000 gp, bringing total cost to 13150 gp)
5. Upgrade mithral chainmail +3 to +4 (+7000 gp, bringing total cost to 20150 gp)
6. Upgrade mithral chainmail +4 to Celestial Armor (+2250 gp, bringing total cost to 22400 gp, the cost of Celestial Armor)
My question is, is this legal?
If it's not legal, is there any way to convert mithral chainmail to celestial armor? For example, I can convert my mithral chainmail +4 to celestial armor, but in doing so my mithral chainmail doesn't translate its mithral property over, and therefore I lose 4000 gp (the original cost of making the armor mithral) on conversion? In other words, the final upgrade costs me 6250 gp instead of 2250 gp, bringing the total price of mithral chainmail being upgraded in piecemeal to celestial armor to 26400 gp?
As this is a PFS character, and I'll be playing it with multiple GMs, I want to make sure my upgrade plan is completely legit under RAW.