Debt, why not? If it's been done by a UK LLP, I haven't seen it.

As for "Equity", I am sure that has not been tried, but of course proportional "Equity Shares" are exactly what I am suggesting could be an optimal new "asset class", with more in common with units in a Canadian Income Trust than anything else.

Inside an LLP is a very strange twilight zone in accounting terms: a Member has an account with an LLP, and "Equity" and "Debt" are essentially continuous.

"The future is already here -- it's just not very evenly distributed" William Gibson