The Independent Parliamentary Standards Authority (Ipsa) said a looser system where politicians took responsibility for justifying their spending to the public would be "simpler" and provide "value for money".
The prospect of a gradual shift could help soothe MPs who are furious over the bureaucracy and costcutting imposed in the wake of the expenses scandal that rocked Westminster.
Last month David Cameron condemned the rules as "anti-family" and warned that they had to change, while backbenchers have been openly calling for the watchdog's chairman Sir Ian Kennedy to quit.
However, there is bound to be concern at the idea of easing restrictions, with research suggesting that only a third of the public trust MPs to file legitimate claims.
A public consultation published by Ipsa floated a number of improvements to the existing scheme, including allowing scores of outer London MPs to claim for running second homes again.
The document suggested funding more travel for MPs' families and increasing the £130-a-night limit on hotels.
But it also raised the prospect that a less rigid system could be introduced in the longer term, with MPs "justifying their own decisions".
Instead of detailed rules, there would be "an expenses scheme based more on a set of principles which do not attempt to cover every eventuality".
"It will need a decision that a system that is easy to understand is preferable to a larger rule book which seeks certainty but necessarily falls short of delivering it," the consultation said.
"It will also require an agreement by MPs that they will take greater responsibility for their claims within the general framework of principles and the agreed budgets.
"If this were to happen, Ipsa would be able to be less demanding. The taxpayer would still be able to obtain assurance that public money was being properly disbursed, since the majority of claims would continue to be published and after-the event auditing would remain.
"Transparency and accountability would be as strong as now."
In his foreword to the document, Sir Ian highlighted the "ever-increasing demand for detailed advice and interpretation of detailed rules and guidance".
"The cost to the taxpayer is considerable," he wrote. "We are clear that the model of how we do business must evolve."
Backbenchers renewed their attack on the watchdog as the six-week consultation was launched this morning. Liberal Democrat Bob Russell told BBC Radio 4's Today programme the organisation was the worst he had dealt with in 40 years in public life, while Tory Roger Gale said the chairman should consider resigning.
But Sir Ian dismissed the idea of quitting, suggesting politicians were just having trouble accepting the "new world".
"Ipsa is doing the job Parliament asked it to do," he said. "We are here for the long haul. There's not an immediate quick fix that's possible."
Under the rules in force before the general election, only 25 MPs with constituencies in "inner" London were not entitled to claim for a second home.
But Ipsa increased that figure to 128 after deciding that politicians did not need extra accommodation if their seat was within 20 miles of parliament, or they could reach it within an hour on the train.
The consultation questioned whether that was "unfair" to the MPs who can no longer claim, pointing out that the Commons often sits until late at night.
MPs are permitted to spend £130 a night staying in London hotels, and £105 elsewhere in the country. Ipsa revealed that the average overnight claim in London was £111.51, but there was also "anecdotal evidence" of difficulties booking hotels for less than £130 at short notice.
Taxi fares can only be reimbursed if they are "absolutely necessary", but some MPs have complained that the definition is arbitrary.
"An alternative approach would be to relax the rules on taxis and rely on MPs to make the judgment about what is reasonable, bearing in mind the current financial climate and the fact that claims for the use of taxis will be published."
Under the existing scheme, MPs can claim for children aged 5-17 to travel between homes. But if the politician's spouse or partner accompanies the youngster, they have to pay their own way.
"Some MPs have argued that this might force children to travel on their own; others argue that it discourages MPs' families from being together and is therefore detrimental to family life," the consultation said.
The watchdog also disclosed that it had complained to the Commons authorities over a new flat-rate charge of £15 for eating in the Members Dining Room. A £10 option has since been agreed, but even that was "still likely to exceed the price of the same meal if bought by a non-MP".
A poll commissioned by Ipsa to accompany the consultation demonstrated the lasting damage from the expenses scandal.
Less than a third of the public trust MPs to claim only for legitimate expenses, according to the poll by YouGov. A further 35% said they had some trust, but not very much.
Leader of the House of Commons Sir George Young said he welcomed the "wide-ranging review".
"The expenses system is there to give MPs the support they need to carry out their jobs, and Ipsa should look again at areas where the current scheme is not adequately doing that," he said. "We support the principles of independent and transparent regulation of MPs' expenses."
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