Budgeting with GnuCash

[John Arrowwood]

Could someone please describe the features of GnuCash for use with 
budgeting?

Here's a summary of what I'd LIKE to be able to do.  Could someone please 
tell me which are doable now, and which would require changes to GnuCash?  
And for those requiring changes, how hard it would be to get those changes?

* Ability to specify a budget amount for each account.
  - the amount is for a given period, e.g. the week, month, quarter, or 
year.  (I'd be happy if it was just months)
  - previous budget amounts are saved, facilitating budget vs. actual 
reports after-the-fact.
* Budget vs. Actual report, single and multi-column
* Budgeting report - multi-column showing e.g. one column per month, with 
'average' for the last column
* Spreadsheet like interface to budget amounts allowing easy data entry and 
scenario exploration
  - alternatively, a report that exports a spreadsheet format which can be 
opened and tweaked
  - maybe with auto-re-import of the spreadsheet after tweaking (yeah, 
right!)
* Flag on transactions indicating that the transaction is 'placeholder' or 
budget
  - allow alternate coloration for placeholder transactions for easy 
identification
  - additional 'balance'...  one that includes placeholder transactions, one 
without
  - alternatively, the field for reconciliation could just have another 
state for 'budget'
* Additional transaction fields
  - Transaction time
  - Receipt?  (flag)
  - Who performed the transaction
  - Date cleared
  - Bank transaction description
  - ???

Is this doable with GnuCash, or would you suggest using something else?

Thanks!