Yes, we could calculate the time until tournament and pop up a warning. The most user-friendly solution would be to do that and show a direct link to troop payment if and only if the tournament duration + current unpaid days is above the limit for troops getting tricky.
Yeah, that's probably best. We'll also almost always be displaying it, since most tournaments are 7 days, and when you add in the aftertour and return, it comes to 8, which is long enough that any unit will at least be complaining.
Another thing to keep in mind is autopayment. Even though it might be reasonable to interpret "you can't do anything" to mean "you can't click on Pay your men", I think many or most people would expect their autopay settings to still work if they don't already know that they won't. Heck, it caught me out at least once.
