What is the difference between "One way would be" and "One way will be"? Can both of them be used for future actions?
In British English, at least, "one way will be" is so peculiar that it might be termed wrong; what does it actually mean? "One way is", however, is entirely normal, as pointing out a possibility. There is a slight connotation that *this isn't what I would recommend, but it's possible", whereas "One way would be" is putting forward a suggestion; but it's only faint.
That would be Mr. Smith. That will be Mr. Smith.
(In either case, the assumption is that it is Mr. Smith who has rung the bell and now waiting to be received.)
We can use "would be" or "will be" in this sense to express a conclusion / assumption.
So, under the condition that you are making an assumption regarding certain future activities or events, there is probably no difference in the two.
One way would be to throw a party. One way will be to throw a party.
There are some more nuances involved. But the above will/would be one way of approaching the issue.
In both cases, presumably the speaker is talking about a way to do something in future time. The use of past-tense modal would suggests a tentative idea for consideration. It usually means something like "here's a possibility; (what do you think)?" and would be appropriate when somebody's trying to solve a problem or come up with ideas.
The use of present-tense modal will on the other hand, typically suggests something established or decided. Perhaps an experiment has been designed already, but not yet carried out, and the participants will be treated different ways.
(Note that grammatical tense and physical time are distinct concepts, which is why past-tense would can signify future time.)