Problems with clearing accounts

I’m still having some issues as indicated One Payment for multiple Invoices

After grouping all the lines on the monthly payment summary, I still have the problem that account_payment_clearing seems to want clearing accounts that disallow party_required.

In the French PCG, when exchange bills are returned to the supplier, the accounting movement
is from 401x to 403x. Then when paid 512x will reconcile with 403x.
(similar in reverse direction using 411x/413x for clients)

Why not allow clearing account with party_required?

Because clearing is not about bill of exchange but about well clearing (see Issue 4225: account_payment_clearing move line creation do not take into account the party_required status of the account - Tryton issue tracker).
So clearing account can not be used to book the same payable and party because it will still make the amount payable to the party. The registration of bill of exchange must be done using another workflow (it can be manual move).

Can the grouping be adapted to put the ultimate move line there instead in order to be selectable from the statement during payment processing? That is, ultimately that is what a large number of our groupings are for - treating monthly exchange bill statements.