I got a 1905 production 1903 springfield this fall. It had a broken but original stock, that I repaired, and was rebarrelled in 1918. Unfortunately the barrel which I thought would be serviceable, I believe is shot out. I was struggling to make hits on my 200yd target. After cleaning and shooting I dropped a 30 cal bullet in the barrel and it drops in about 1.5"-2" before stopping.

So this leads me to a conundrum. I don't really want to buy a new criterion barrel because I like the vintage aspect of it. But at the same time it's not the original barrel anyway and the repaired stock probably greatly reduces its value for what it is.  Then just the aspect as far as my collection goes, this thing isn't going to see a ton of use. Maybe 50-100 rounds a year.

Are there options to improve the barrel as is or is replacement the only option?

If you can get on the CMP forums in the bolt action for sale area they sometimes have barrels for sale.

This was a thought I had. Wasn't sure the max length that's good for though.

you might try fatter cast bullets. Lyman 312299 or maybe bigger 314299.

very popular mold for milsurps.

Contact Taylor Machine of Pullayup (sp) WA and have him reline the barrel.  Lot cheaper than rebarrel.  He did an 1895 Win in .30-40 for me.  If you don't know it is lined, you won't notice the liner.  Accuracy is as good or better than an 1895 should be.  The liner has been serving for over 10 years and is going strong with about 500 rounds a year.

Last time I checked you couldn't reline a high pressure round like the 30-06.  

OP:
Either counter bore or buy a new-to-you 1903 barrel and switch out.  You can still get loose 1903 barrels for a reasonable price.