Not sure if you want them rotated and perspective correct - but if you want them as billboard labels - maybe something like this:

[source]

Matrix inv = Matrix.CreateScale(1,-1,1);
basicEffect.World = inv;
basicEffect.View = Matrix.Identity;
basicEffect.Projection = projection;

spriteBatch.Begin(0, null, null, DepthStencilState.DepthRead, RasterizerState.CullNone, basicEffect);
i=0;
do {
Vector3 position = billboard.pos;
Vector3 viewingSpacePos = Vector3.Transform(position, view * inv);
Vector2 origin = spriteFont.MeasureString(billboard.text) / 2;
const float size = 0.4f;
// last parameter is Z coord:
spriteBatch.DrawString(spriteFont, billboard.text, new Vector2(viewingSpacePos.X, viewingSpacePos.Y), Color.White, 0, origin, size, 0, viewingSpacePos.Z);
i++;
}while(i<num_billboards);
spriteBatch.End();

[/source]

Also may want to adjust pixel offset by half pixel in projection: projection = projection * Matrix.CreateTranslation(-0.5f, -0.5f, 0);

Why not transform just the "anchor" point of the text (usually the bottom-center of a line, or the top-left of the leftmost character, or something) to get a screen-space position for the text, and then draw your glyph-sprites relative to that position using Spritebatch. Round to the nearest pixel after calculating the screen-space position to reduce aliasing effects.

Unless you need your text to have size and rotation appropriate for billboarded objects in-world? Then create a billboard transformation matrix appropriate to the anchor of your text, and then just lay out your glyphs within that single billboard model space.

I'm not sure what you're asking for with "perspective text", nor why you think it's too much work to transform individual glyphs before passing them to Spritebatch. It sounds like a necessary step to get any individual sprites into the scene.