(Reuters) - The U.S. Senate will resume debate this month on financial regulatory reform, but a handful of changes some see as crucial are not on the table.

Below is a summary of five proposals excluded from a bill approved last month by the House of Representatives, and from a draft bill being debated in the Senate Banking Committee.

* MORTGAGE ‘CRAMDOWN’:

In a proposal backed by homeowner activists and many Democrats, bankruptcy law would be rewritten to allow judges to change the terms of mortgages for distressed borrowers in bankruptcy court. Known as mortgage “cramdown,” the idea is opposed by the banking industry, which won a victory last month when an amendment that would have added “cramdown” to the House’s financial regulation reform bill was defeated.

The House had approved a “cramdown” measure in March over the objections of Republicans, but it died in the Senate.

Under present law, bankruptcy courts may reduce many forms of debt for struggling borrowers -- including for a boat, car, vacation home or family farm -- but not a primary residence.

Cramdown would help stem the home foreclosure wave continuing across the United States, its advocates say. But opponents say it would raise costs for everyone and divert capital from the mortgage debt market.

* NEW CREDIT RATING AGENCY BUSINESS MODEL:

Tighter regulation of credit rating agencies -- such as Moody’s Corp, Standard & Poor’s and Fitch Ratings -- is proposed by both the House bill approved last month and the bill under debate in the Senate.

But neither calls for basic change in the so-called “issuer pays” business model that critics say presents credit rating agencies with a glaring conflict of interest.

Most of the agencies’ revenue comes from the issuers of bonds and other debt instruments that the agencies evaluate and issue ratings on. Critics say that can mean that ratings are colored by the agencies’ need to win and keep business.

Congressional aides said lawmakers could not find a way to change that business model without destroying the industry.

Rating agencies were widely blamed for failing to spot problems in the subprime mortgage market and other areas ahead of the 2008 global financial crisis.

* MERGING SEC AND CFTC:

The Securities and Exchange Commission and the Commodity Futures Trading Commission regulate financial markets so inextricably linked that critics for decades have said the two agencies should be one.

A year ago, when the Obama administration took over and the financial crisis was in full swing, a CFTC-SEC merger looked like a possibility. But as the House of Representatives began hammering out a politically realistic set of post-crisis financial reforms, the merger slipped from view.

Neither agency wanted it since it would threaten jobs and turf. Financial services industry lobbyists were divided, with some favoring a merger and others against it. Some policymakers saw virtue in preserving competition between the agencies.

In the end, legislators said, in a perfect world, the two agencies would be combined, but that just isn’t Washington.

* FIXING FANNIE MAE AND FREDDIE MAC:

The two giants of U.S. mortgage finance -- Fannie Mae and Freddie Mac -- need a major overhaul. That much both political parties in Congress can agree on.

But the consensus pretty much ends there.

The Obama administration has said it will sketch out a reform plan for the two agencies in February.

So contentious is the struggle over fixing Fannie and Freddie that Democrats opted to shelve it for now, excluding the issue from financial regulation reform bills in the House and Senate. They pledged to deal with it later.

Fannie and Freddie together own or guarantee half of all U.S. mortgages. Both were seized by the U.S. government and put into conservatorship in September 2008 at the outset of a financial crisis that rocked capital markets worldwide.

* USURY CAPS:

Several congressional Democrats have introduced a bill to cap credit card interest rates, but the measure is not included in either of the main House or Senate packages.

Another bill offered in the Senate last year would cap rates at 36 percent for all consumer credit -- mortgages, payday loans, car title loans -- not just credit cards. It is not included in the two main legislative packages either.

Some states have usury laws. Both the main House and Senate reform packages have provisions saying how often and how far federal regulators may preempt, or block, state consumer protection laws, which can affect state usury statutes.