personally i have simply been planning to buy an alanog devices DDS module, hook it up to an arduino module, and then add my front end and power supply and be done with it,
however before that i settled on building a voltage controlled oscilator, as its much easier to get wider frequency ranges over them, the pot degrading effects it less, and the number one key thing, the amplitude does not vary with frequency
, it gives you square and triangle, then using a multistage triange to sine converter to get the same constant amplitude out of it, (only diodes and resistors) one can get good square tri and sine at constant amplitude over a decent range with only a quad op amp (2 for VCO, 1 for output buffer and other possibly as input buffer or secondary output) with the tri to sine being the largest component wise thing of the bunch
if you start using some of the integrated ones you will find hell from integrators killing your amplitude and having to use all manner of correction circuitry,