just a question

I wanted to know if there is a way for this situation.
France en Spain are allies and France and England are in war
When England attack France could France ask Spain for help
Only France has to pay Spain for his help, like;
Spain could send 5 units and France has to pay them let’s say 5000
Or Spain send 5 strong units and France has to pay 10000
Or Spain send 10 strong units and France has to pay 100000
And so on and so on how much ways is how long you wanted to make a deal.
You could think about;
5 units normal strong costs 3000
10 units normal strong costs 6000
15 units normal strong costs 10000
5 strong units cost 5000
10 strong units cost 10000
15 strong units cost 15000

And how far the allies are that’s is the way you have to pay if they are on time for help.
And you could think, to play this way back.
If Spain is asking France for help.
So you could win some money or lose a City or Castle.
Only is it possible to make something like this or better.
I have seen that it is possible to send Crusaders to a special City or Castle.
Also I have seen that the pope could pay you some money.
Make a combination of it and give the possibility to place it in where you can make the choices ;
Of a Diplomat or Princesses
Sorry for my English it isn’t easy for me to explain what I wanted but hope that you understand it and for the best hope that you can use it and wanted to use it.
This is thinking a way to make your Bellum Crucis 5 a little better than it is already.
Please let me know what you think about this.

Regards J.P.