What are you trying achieve with non standard bits?
There are a range of different angles available already for the Leigh jig. For half blind or lap dovetails they run from 18 degrees to 8 degrees, they're dependent on wood thickness but there's enough overlap that you usually have a choice.
If you're trying to get the most "hand made" look possible then 8 degrees is the one to go for (that's about 1:7 in slope terms), but even more important is to use a drawer front that's about 24mm thick and use the absolute maximum depth of cut you can, Leigh give this as 19mm but you can actually go a little bit deeper, say 19.5mm to 20mm. The reason depth of cut is important is the deeper you go the narrower will be the "throat" of the tail, and it's that which usually distinguishes hand cut dovetails.
One other option you have with the Leigh is to set up to just cut the pin board, then you can go right down to a "needle point" or "London pattern" dovetail, but you have to transfer the markings from the pin board to the tail board (which I don't like) and cut the tails by hand (which is no big deal).
The Woodrat goes a different route, HSS cutters with a 1:9 slope, allowing a much tighter "throat". The problem (besides snapping cutters) is that 1:9 looks a bit weird to my eye, especially as the fashion at the moment is to go for wider slopes. Many well known makers have abandoned the traditional 1:8 in favour of 1:7 or 1:6, and some adventurous types are going even further to 1:5 or an eye popping 1:4.
Having said all this, cutting dovetails by hand just isn't that difficult unless you're doing something well out of the ordinary like secret mitred dovetails, or through dovetails with a mitre in 50mm or thicker stock. If I've only one or two drawers to make I usually make them entirely by hand, if I've a few more then I'll cut the tails on the bandsaw and remove most of the pin board waste with a router, which really speeds things up. But dovetails themselves aren't actually that tricky by hand, it's fitting the drawer for a piston fit that's the hard part!
Good luck!