Fritzbox 7140 annex A: Alternative programs/firmware?

[technoboy]

I have a Linksys/Sipura SPA3000 and I am very happy with the way it operates. I like the dial plan set up and I can make it do all I want.
I also have a Fritzbox 7140. I find the dialling experience a pain . The so called 'quick dials' are far too long, all numbers beginning with * are routed to internal operations, a # has to be appended to each number dialled, there are no number conversion capabilities in the dial plan, etc., etc.
These are just a few of the things I don't like.
Hence I want to change the way in which the Fritzbox operates. If I could bypass completely the fixed dial rules and route directly out to Voxalot then this would be satisfactory, then I can set up voxalot to route as I please. Alternatively a complete reflash with different firmware might be a solution. Any reference to reflashing, with alternative firmware, seems to end on a page in German. Dealing with technical things, in a language I don't understand, is no use to me.
Any suggestions as to how I can proceed?