If you have flat land, going with catguy's suggestion of a moco
sounds good. If you have any kind of hills at all, however, I think
you'll be significantly lacking power with an H. I've used my Super
W6 on a 9' haybine a few times when I was in a pinch. Walked away
with it effortlessly on flat land, but struggled on hills, and
that's a lot more power than your H. Really thick legumes can also
draw a lot more power during the crimping process if the rolls are
set tight.
I think you're also a little light for a disc mower. Even if you
have the power for a smaller (5' or so) disc mower), I think an H
would be a little light for the disc mowers I've used.
The sickle mower sounds like a good option. We still cut 60-70 acres
on one of our farms with a sickle mower. Certainly more finesse
involved, but if it's in good shape and registered correctly you
should do fine once you get the hang of it. I can mow at 8 miles an
hour with our 9' sickle mower when things are going good. Not disc
mower speeds by any means, but still fast enough to knock down some
hay in a hurry.
See my post in this thread I made a few weeks ago on different
types/makes of sickle mower (though I made a mistake in it: the New
Idea sickle mowers don't have the same lift mechanism as the IH):
Sickle Mower Considerations