Hello,
In general, if it's not part of SVG and there is no fall back, then no.
Wouldn't it be a good idea to (first) work out a specification of gradient meshes for the W3C SVG WG? Looking through the archives it seems to me as if they didn't even yet agree on the general topology...
PDF (and PS level 3) for example knows these gradient types:
• Function-based shadings (type 1) define the color of every point in the domain using a mathematical function (not necessarily smooth or continuous). • Axial shadings (type 2) define a color blend along a line between two points, optionally extended beyond the boundary points by continuing the boundary colors. • Radial shadings (type 3) define a blend between two circles, optionally ex- tended beyond the boundary circles by continuing the boundary colors. This type of shading is commonly used to represent three-dimensional spheres and cones. • Free-form Gouraud-shaded triangle meshes (type 4) define a common construct used by many three-dimensional applications to represent complex colored and shaded shapes. Vertices are specified in free-form geometry. • Lattice-form Gouraud-shaded triangle meshes (type 5) are based on the same geometrical construct as type 4 but with vertices specified as a pseudo- rectangular lattice. • Coons patch meshes (type 6) construct a shading from one or more color patches, each bounded by four cubic Bézier curves. • Tensor-product patch meshes (type 7) are similar to type 6 but with additional control points in each patch, affording greater control over color mapping.
(http://www.adobe.com/devnet/acrobat/pdfs/pdf_reference_1-7.pdf pg. 304)
AFAIK SVG only has "Type 2" gradients, since PDF's "Type 3" allows not only ellipses and their center but arbitrary circles.
"Type 7" Tensor-product patch meshes seem like the best format to me, depending on the output format it can be rendered as types 6, 5, 4, or blurred blobs of color.
The UI should be like Illustrator's, i.e. allow generation of a rectangular n*m grid, subdivision, and the gravity brushes to deform the mesh. Also, in addition to pulling on path segments using the mouse and thereby adjusting the 2 control points, it should be possible to pull on a patch and adjust its 8 control points.
Just my 2ct.