Will garden peas graft onto a legume tree?

I love peas. After 6 years of selection starting with English garden peas, I have a landrace that will grow during our summer (upto 45C).

They take 40 days from seed to eating and taste fantastic. But germination rate is about 50% & I only get a handful of pods per plant, before the plant just stops flowering, wilts, and dies. And they need a fair bit of water.

Leguminous tree Leucaena Leucocephala grows easily as long as it gets some help with irrigation in its first year. I've got this vision of having a tree with thousands of garden pea pods growing on it, producing all year round for many years in a row. I know you can graft peas onto beans and vice versa, so could it be possible to graft them onto a leguminous tree? Some googling hasn't returned any evidence either way. Is this a fantasy or should I pursue it. Don't just say "give it a go and you'll find out" because with no grafting experience I will not know if failure is due to it being a non starter idea, or if it's simply down to bad grafting skills.

Garden peas (unless you mean pigeon peas?) are annuals, so I don't think grafting would be a huge benefit.  Growing from seed is also very easy.  Do you have unusual soil pests?  If not, why bother grafting at all?

To my knowledge, only cacti will graft among quite unrelated types.  You can graft across genera in the pomes of the rose family but only a bit: some European pears will work on quince but at least half and all Asians won't.  Loquat will work on quince but the dwarfing is so extreme that there may be delayed incompatibility.  Medlar grafts (on pear, hawthorn, or quince) are buried so that the medlar scion will eventually grow its own roots because the grafts often fail within a decade.  "Winter Banana" apples tend to work on pear, but most apples won't.  Sorbus hybrids failed for me after 1 year on pear.

With the new phyllogenic taxonomy, legumes are being rearranged, but Leucania traditionally is in the mimosa subfamily and peas in the bean subfamily.  They have very different floral geometries and are unlikely to be close relatives.  To me, this is a non starter.