Like PhaedrusXY said, if the Ur-Priest is allowed you can probably get away with lower caster crafting levels on items. And why not, if the DM bars you from making lower caster level items then he should wave the caster level requirements on craft staff and such. The Ur-priest is certainly a hard road to take in Faruen though, you will end up in the living wall or serving in that city for sure. Following the dead deity technique probably wont get you out of it, but it might allow 5x/Ur-priest 2/Runecaster 8/Heirophant 5
The same can be said for the Sublime chord. It is quite possible to build a bard 1/Wizard 9/Sublime chord and pick bard as you arcane class to add to your caster level. That means you can make level 4 and 5 spells with a caster level of 2. And if you allow stuff like southern magician to produce arcane spells, you could go divine bard 10 dropping those sublime chord caster levels to 1. Knowing this any sublime chord should be able to cast level 4 and 5 spells with a caster level of 1 or 2.
The only problem you run into is acid test rules. You can make items that give bonuses cheaper than the DMG guideline prices such as the continous use True Strike example. Continous level 2 +4 ability score spells would cost 2x2x2000=8,000gp, half the price of a standard +4 item and slotless to boot. Of course you can argue that the rune is also much more vulnerable than a standard item. So you might want to stear clear of any standard type bonuses that are too cheap if your DM will care.
So is there much of a reason to take levels 9 and 10 in the class? Level 9's +1 against dispeling is not bad, but level 10 +1 caster level does not seem like a must have. Only seems really useful if you are going with epic progression on the class, and probably not then either. I am partial to Savage Bard 4/1x/Ur-Priest 2/Runecaster 8/ heirophant 5 if you can get over heirophant and ur-priests wording working together. I would think two levels of spell power would work better if you really want those bonuses. Practiced spell caster could also help that along with a bead of karma to boost your caster level when you make runes. They just so happen to both last 10 minutes. Magic Artisian is a given.
I wonder if you got a spellblade for erase and all the dispel spells, would it work on your equipment? Targeting your equipment probably does not count as targeting you, but it would be funny if the spellblade weapon enchantment made all your runes safe baring disjunction.
I also wonder how runemaster would work with Craft rune circle. You can make a small rune circle that has the same effects as any magic item at 1/8 the cost. One hell of a cheap trap.
Costs:
1) Ur-priest caster level can half cost if you are not worried about spell level.
2) Persistent Rune does not have the standard spell duration multiplier the DMG states for custom items (rounds/level 4x cost)
3) Rune circle costs magic item's price times 1/4.
4) Small 5 foot square cuts costs 1/2
So you figure 1/8th the price for a 5 foot squre trap, not including the price mode if it is persistent and with a short duration. Then you factor in 1/2 cost to craft and possibly master artisian, you end up with a really cheap trap.
