Before considering a tankless, what is your expected max draw and what is the coldest incoming winter water temperature? The max gallons listed in the big print on a tankless assumes some fairly warm incoming water compared to some places in the US. Mine can be barely above freezing during a cold snap in the winter, and to get any decent volume of hot water would need a huge tankless. You may need to upgrade your supply and almost certainly the line to that WH to go tankless to be able to supply it properly. A too small gas supply line will compromise the operation substantially.
If you're planning a large soaking tub or a multiple jet shower arrangement, 50-gallon electric (and probably gas, too) is too small.
While it's nice to have the WH close to the bath for speed of hot, with the addition of a recirculation system, it can be relocated to where it may be more convenient. Why take up space in your new bath for the WH?
But, the easiest conversion would be to just go electric. Keep in mind that the recovery rate is lots slower than your current gas unit, and that may affect your sizing decision - a direct swap in size compared to the gas unit may not suffice.
Forget about an electric tankless.