I'll start by saying if this is already possible, I'd love it if someone told me how.
Let's say I have a closer such as Niggeling with great IP/G and can easily get 2 or more innings saves if needed, but at the same time, I want him available for 50-60 games if possible.
I would like him to be available in the 8th in save situations, but I don't want him to START the 8th.
For example: We are up 4-1 and Setup A gets a couple runners on with 1 out, bring in Niggeling for the 5 out save! If Setup A does his job, Niggeling pitches the 9th and all is well.
If something was added to inning available, something like 7+ or 8+, meaning they could come in later in that inning in high leverage situations, but won't start the inning. Could even be a check box next to Use Closer only in save situations, another box like: Bring in closer early in high leverage situations. This could apply if multiple runners on base, including the tieing run, things like that. If I have Niggeling, I would love that options, if I have someone like Rivera with 1.05 IP/G, I would leave this box unchecked and he will only go for 3 out saves.