I also would like to renew my support for this request.
We just came back from hiking 2 weeks in north-east France, Lorraine, Vosges and Alsace.
Locus was our constant companion and performed admirably, thanks Menion!
BUT the state of off-road OSM data is still very inconstant there. There were areas where for >50 km there was absolutely nothing on any OSM-based map except some car roads, whereas Google maps has almost all of the tiny footpaths and forestry roads there.
Frankly, without Google maps we would have been lost (although we got lost twice when Google maps thought there was a footpath, when in fact there was none...).
What I am saying is that for France, the superb quality of the Géoportail/IGN topo maps seemingly can not be replaced by any free alternative at the moment, at least not for the off-road hiker.
So I think if it is doable at all, it would be worthwhile to include those French IGN maps into Locus. They will be unsurpassed for quite some time.