I would doubt very much that anything in Indiana can be upgraded from a B-1 to a B. There are some other options, depending one the station owner's goals.
1. Change the city of license & move the transmitter site to cover more population or a bigger city. You can change the city of license for an FM as a minor change IF you meet the following conditions:
A. You would not be removing that city's only radio station (that is, there is another AM or FM station, even non-com, licensed to the present COL);
B. The new site meets the minimum separations under the rules, or there is a site that meets these requirements, and the new proposal covers the new city of license with a 70 dbu signal.
C. The new site must be "mutually exclusive" with the existing site (that is, it must be close enough to the old site that you can't have two stations).
D. Moving from a small town to a metro area brings other legal considerations in play, requiring special showings (called a "Tuck" showing).
For an example of this, look up the minor change application for WPFX, North Baltimore to Luckey, Ohio, BPH-20090915ACX
2. If the "open area" is too small to allow much moving around, depending on where in Indiana the station is, a higher antenna may provide better coverage. In "pool table " country (northern Indiana), probably won't make much difference. In hill country closer to the Ohio river in southern Indiana, a higher antenna may provide enough of a margin to clear a hill and get more signal into some valley community.
3. A section 73.215 short-spaced site may make sense if the present, fully-spaced, site is too far from the population they want to serve. E.G. 13 kw @ 300 ft AHAAt may work a lot better if the antenna is right above town, rather than 25 KW at 300 ft AHAAT some dozen miles out of town.
As Scott mentions, a consultant can fire up his fancy computer program and give some quick answers on what can or cannot be done.