After years of success in the second-tier Football Championship Subdivision (formerly Division 1-AA), UMass decided to join the top-flight Football Bowl Subdivision (formerly Division 1-A) partly because school officials believed the team’s affiliation with the Colonial Athletic Conference would grow costlier amid a membership shuffle. The decision posed two crucial challenges: playing home games on a larger stage than the 17,000-seat campus stadium and joining a suitable FBS conference.

By opting for Gillette, UMass deferred a debate over financing a new stadium — a project that would cost hundreds of millions of dollars, including road improvements — and negotiated a deal that provides the school financial safeguards in case of poor attendance in Foxborough. In exchange, the school granted the Kraft family, the stadium’s owners, a greater share of the revenues if tickets sell well.

“If there turns out to be a lukewarm reception in the next few years, then the university doesn’t have much of a risk,’’ said James Karam, a UMass trustee who was chairman of the board when it endorsed the upgrade. “That gave us a great opportunity to experiment with this.’’

Under the five-year agreement, the Krafts will control ticket, concession, and merchandise sales, and equally split with UMass the first $300,000 in ticket revenues per game. The Krafts then will retain the amount above $300,000 to cover their costs of staffing and operating the stadium, an estimated $125,000 per game. Should additional ticket revenue exist, UMass and the Krafts would split it evenly.

The arrangement effectively guarantees the university will earn at least $150,000 per home game, even if attendance lags, because the school will not be liable for operating expenses. But the greater the attendance exceeds about 21,000, the more the Krafts will gain than they would have under a standard lease agreement, according to UMass officials.

“If we have great success, then obviously we traded some things off,’’ athletic director John McCutcheon said. “But we wanted the comfort level at the low end.’’

The deal requires UMass to play all its home games at Gillette in 2012 and ’13, then play at least four games a year there through 2016.

“We need a venue we can recruit the best players in America to,’’ the team’s new coach, Charley Molnar, said in a news conference. “Playing at Gillette is a perfect piece of the puzzle.’’

Finding another piece proved more problematic. Stymied in trying to align with the richest FBS conferences, UMass settled for paying $500,000 to join the Mid-American Athletic Conference, a lower-level FBS affiliate with a small television contract and little national exposure.

Unlike New England’s other FBS teams, BC and UConn, whose football teams turn a profit, UMass chose a formula that, analysts say, could be a losing proposition.

“I wish them luck, but I just don’t see how it works competitively, financially, or educationally,’’ said Andrew Zimbalist, a Smith College professor who is one of the nation’s leading sports economists and has consulted for the NCAA. “I hope I’m wrong, but it seems like kind of a farce.’’

By all accounts, the key to cashing in on college football is joining one of the six major FBS conferences that automatically qualify for championship bowls and command lavish television contracts. BC did so with the Atlantic Coast Conference, UConn with the Big East.

While BC reaps a reported $17 million a year from the ACC’s television deal, for example, UMass stands to gain about $75,000 a year in MAC television revenue.

UMass officials said they lack the major funding BC and UConn received to build profitable football programs. As a result, their best hope is building the Minutemen into a regional power worthy of joining a big-money conference.

“That’s got to be the goal,’’ Karam said. “Ultimately, it’s about TV revenue.’’

Karam, an appointee of former Gov. Jane Swift, joined several of former Gov. Mitt Romney’s appointees, including Carlin, in providing impetus for the upgrade. Ultimately, the full board, including Gov. Deval Patrick’s appointees, endorsed the plan.

The board’s new chairman, Henry Thomas 3d, said the trustees vetted the proposal and deemed it a “sound and reasonable’’ effort to burnish the university’s stature.