This is incorrect. Changing only the inner chainring, the large/large combination will still be the same, and so the chain must remain the same length. You might get excessive droop in the small/small combination, but you should never use it anyway so it's not an issue.

I agree that changing the chainring to a 26 would be the way to go. You'll use the same cassette, so you'll still have the closer ratios. Plus, 26/25 is lower than 30/28 (if you decided to swap on a 12-28 cassette.)