A 1x per week protocol runs straight into a detraining effect. It's not in any way ideal and it's largely based on misunderstood science. Increasing frequency is highly preferable even to 2-3x per week. The one issue people run into with increasing frequency is that they do the same workout more often - so if shooting for 2x per week they end up doubling the total volume. Well this is a major problem and why this blows up in people's faces. A better way is to use frequency to distribute your existing volume and then see over time if you can handle or require more. Example: You do 10 sets of squats for legs 1x per week - change this to 5 sets twice a week - total volume over the period is constant but frequency is increased. Now with 5 days rather than 7 this isn't as severe as doubling volume but make no mistake, if your workout protocol doesn't change you are significantly increasing volume. Maybe you can handle that and maybe you can't (depends on your level of conditioning and what your current tolerance for volume is) but you asked for possible issues and this is the key one.