Before writing up a policy, I would take a step back and look at the profile of the employees who will travel and the nature of their travel.
1. Who are the employees? Are they senior professionals and what sorts of work do they do? Do they have marketing and business development responsibilities?
2. What sorts of competetive pressures does your company face? It's fine to require your people to stay in a Motel Six and take Super Shuttle, but that won't work if the competitor down the street can at least make all other things equal and pay for a Four Seasons and car service.
3. Is travel largely to specific destinations where you have a good handle on expenses or is it far flung? If 95% of the travel is to five cities, you can be pretty specific without hemming people in. If travel is worldwide, there needs to be more flexibility.
4. What sorts of travel? Is 95% of it short-haul domestic where it simply doesn't pay to even consider F or is 95% of it ultra long-haul international where F/J really is important?
Once you have the basics down, you can then turn to the specifics. Why worry about whether there needs to be a per diem supplement in Omsk if nobody in your company ever has or will travel there?
Business development may be an important issue. It's one thing to worry a bit about what are reasonable allowances for an individual's meals to keep them fed and content on the road. But, if having them do some entertaining on the road is part of the job, there are many other considerations. If some of this is overseas, there are FCPA and other anti-bribery and even cultrural issues to consider.
Finally, receipts are an issue. If you are solely a US-based company where all of your employees as US-based, take a look at IRS rules and start with those as a minimum. If the IRS only requires receipts for <$25, why are you requiring receipts for <$25 from people you trust with $ Millions in new business?
Finally, do a bit of looking at what all of this costs. Time is money. The example above where an individual stuffs envelopes with paper receipts and then sits at their desk and fills out an expense form which then has to be processed by someone else, can't possibly be cost-effective if it includes items of minimal value.