FX2 (TFX2) is suppose to be an ideal stand developer. The formula which incorporates metol prevents speed loss, and glycin which inhibits streaking. It is an acutance developer and generally used with slow to medium speed films. If your looking to vary exposure on a roll within a stop or two, I've had luck with Diafine, but it's not the best developer for all films per se'. With Foma it might just be the ticket. It does last a long time and it's basically temp insensitive within a range which is nice.