Slightly related question.
Can a deal be contingent, for instance A gives B a card and B gives A mercs for each cp over 2 on that card?
No contingences; specific items/actions stated by first power and agreed/denied by the later power in impulse order.
<Ed. to add workaround to the contingency problem in declarations>
Attempting variable conditions on negotiations
Normally, the first party would state the terms and the 2nd party confirms/denies them.
In this example as written, no as there can't be conditional statements like this.
Workaround- England would state multiple conditions as follows:
1. the 'space' and the card from England to France
2. France sends 1Merc to England
3. France sends 2Mercs to England
4. France sends 3Mercs to England
France on their end would:
1. Agree to #1; space and card are given (now France sees what they got)
2. France agrees to one of 2 thru 4; or denies them all.
Of course, England has no recourse if France short-changes them on this deal; so buyer beware etc. on this type of exchange.
I hope that this 'deal' is not part of an attempted Sue for Peace later in negotiations by England; you don't state war status of the two. FYI this has now been rendered illegitimate in the 2017 re-write.
Anyhow, that's the only way I know of that you can work out this type of deal. Just make it clear that they (the terms) are not grouped together; that they are to be 'individual' items; there's no way to do this type of thing as a 'grouped' deal.