I don't have much of a legalese background, so I won't try, but I do my best to give my input.
Nearly all assets are quiet simple, they have a price they start at, they say they'll pay a certain % or static dividend.
Most should have some clause for a payback price if something goes wrong.
Two thing I suggest;
1)
I think it will help if all contracts are tied to a system which tracks if the basics are occurring, like dividends being paid out for a set amount or a % of, or customised based on various api figures, at the set interval, daily, weekly, monthly, twice a week etc.
More details need to be given surrounding basis for late payments, non-payments and in the event of stopping the share/bond, the buy back price due to this breach in contract, with time frames and penalties for any/all of them.
Securities can be both fixed dividend amounts and ranges and we have to consider moving to an automated method. Those with a dividend which could vary from 1-2% for example, would either have to make sure it's value is set to something that is valid in the contract before each pay out.
This would make it so GLBSE itself can trigger dividend payouts, instead of it having to be manual trigger. I don't run a security, so to me it has always appeared to be operated manually, rather than on auto. So aslong as their is bitcoins there, it pays out exactly as the contract states it should.
If dividends fail to be paid out, due to lack of funds, it's an automatic flag for notification something is wrong. Then it's upto GLBSE to warn him/her about a potential failure in their contract agreement. No action needs to be taken if it is fixed quickly and is within their terms to allow for penalties to be paid and is. But once outside the timeframe, then action to roll down, moved to the black market should occur, if the owner of the asset doesn't cooperate. What to do after that, I don't have any hard line advice for.
2)
Also it might be a good idea to add something that, if a stock usually pays out dividends out every 168 hours days (7 days), if you bought it less than 42 hours before it pays out dividends, you don't get included in dividend payouts (1/4 of the dividend period). Likewise a daily dividend would require you bought it 6 hours before dividend payout.
This helps the owner of the assets and prevents unnecessary payouts on investments that haven't really had time to be invested.
It would slow down people from doing quick buys and sells just for the dividends. As far as I'm aware this is not in place on GLBSE, but they do use such a system in places like the NYSE for exactly that reason.
I can offer my insight on some of these by my personal experience running an Asset, But the others can also chime in.
Some of the contracts say the do not do timed payouts, I know of one the withholds that right and payouts out ~6 days due to market selling of Assets to pay dividends.
The method your describing on Dividend percentage reminds me of a Ponzi payout. The Divdend on normal assets are Profit of that time period. My profit Depends on my Pool Luck,Mining Costs, and uptime rate(percent of time my rigs are running correctly). Due to pool luck and what pool i use and difficulity, payout method PPS,Pro my dividend will change every week and never been the same.
Share Buyback or Bond Buyback is part of the contract and can not be forced on contracts that do not allow them. But a Asset Default where the asset is sold off and then the share holders are paid a final payment is very common.
The Dividend payout is always manually paid because unless your asset is running with a reserve to help pay out a min payout, the dividend amount will change every week.
What I do is have a public dividend address where the dividend sits for a week before payout. You could have a Dividend Payout Only Address where BTC could be sent for automated Payout as a dividend.
One of the problems is that is Lumps all coins for Sold assets into the Asset Account, and any Dividends are paid into this account.
I transfer all sales of assets payments to an Asset Sales Public Address to allow the public to see how much BTC are coming into the company, in the current setup this is hidden to the share holder.
This helps a little bit in accountability to allow people to follow the bitcoins.
It all depends on how the contract is written in what event does a default happen and what is the procedure to follow.
As for the holding time required before dividend payment, I think my contract says if you hold a share at payment point you will get a dividend. If people want to Dividend trade my asset buying before and selling after that is fine by me.
I think it effects assets more than pay monthly vs weekly.